diff --git a/.gitignore b/.gitignore
index f71b3c03..85098ddc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@ Gemfile.lock
 
 tmp/rubycritic/
 /.bundle
+.ruby-version
diff --git a/.travis.yml b/.travis.yml
index 840a5117..24c38467 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,7 @@ env:
     - PLUGIN=redmine_hourglass
     - REDMINE=test_redmine
     - TRACE=--trace
+    - RAILS_ENV=test
 
 matrix:
   include:
@@ -18,12 +19,10 @@ matrix:
       rvm: 2.0.0
       env:
         - REDMINE_VERSION=3.2.9
-        - DATABASE=SQLITE3
     - name: Ruby 2.0 / Redmine 3.3
       rvm: 2.0.0
       env:
         - REDMINE_VERSION=3.3.9
-        - DATABASE=SQLITE3
 
     - name: Ruby 2.1 / Redmine 3.3
       rvm: 2.1.10
@@ -51,31 +50,29 @@ matrix:
       rvm: 2.3.8
       env:
         - REDMINE_VERSION=3.4.1
-        - DATABASE=SQLITE3
     - name: Ruby 2.3 / Redmine 3.4.9
       rvm: 2.3.8
       env:
         - REDMINE_VERSION=3.4.9
-        - DATABASE=SQLITE3
 
+    - name: Ruby 2.3 / Redmine 4
+      rvm: 2.3.8
+      env:
+        - REDMINE_VERSION=4.0.2
 
     - name: Ruby 2.5 / Redmine 4
       rvm: 2.5.3
       env:
         - REDMINE_VERSION=4.0.2
-        - DATABASE=SQLITE3
 
     - name: Ruby 2.6 / Redmine 4
       rvm: 2.6.1
       env:
         - REDMINE_VERSION=4.0.2
-        - DATABASE=SQLITE3
 
   fast_finish: true
   allow_failures:
-    - env:
-        - REDMINE_VERSION=4.0.2
-        - DATABASE=SQLITE3
+    - rvm: 2.6.1
 
 before_install:
   - source .travis/clone_redmine.sh
diff --git a/.travis/clone_redmine.sh b/.travis/clone_redmine.sh
index a58aa9f8..6b9b78da 100644
--- a/.travis/clone_redmine.sh
+++ b/.travis/clone_redmine.sh
@@ -48,11 +48,11 @@ fi
 ln -s "$PATH_TO_PLUGIN" "$PATH_TO_PLUGINS/$PLUGIN"
 
 case $DATABASE in
-  SQLITE3)  cp $PATH_TO_PLUGINS/$PLUGIN/.travis/sqlite3_database.yml config/database.yml
-            ;;
   MYSQL)    cp $PATH_TO_PLUGINS/$PLUGIN/.travis/mysql_database.yml config/database.yml
             ;;
   POSTGRESQL)
             cp $PATH_TO_PLUGINS/$PLUGIN/.travis/postgresql_database.yml config/database.yml
             ;;
+  *)  cp $PATH_TO_PLUGINS/$PLUGIN/.travis/sqlite3_database.yml config/database.yml
+            ;;
 esac
diff --git a/app/controllers/concerns/boolean_parsing.rb b/app/controllers/concerns/boolean_parsing.rb
index bbd02d31..d15e4513 100644
--- a/app/controllers/concerns/boolean_parsing.rb
+++ b/app/controllers/concerns/boolean_parsing.rb
@@ -4,7 +4,11 @@ module BooleanParsing
   def parse_boolean(keys, params)
     keys = [keys] if keys.is_a? Symbol
     keys.each do |key|
-      params[key] = ActiveRecord::Type::Boolean.new.type_cast_from_user(params[key])
+      if Rails::VERSION::MAJOR <= 4
+        params[key] = ActiveRecord::Type::Boolean.new.type_cast_from_user(params[key])
+      else
+        params[key] = ActiveRecord::Type::Boolean.new.cast(params[key])
+      end
     end
     params
   end
diff --git a/app/controllers/hourglass/api_base_controller.rb b/app/controllers/hourglass/api_base_controller.rb
index c37de604..a30740d5 100644
--- a/app/controllers/hourglass/api_base_controller.rb
+++ b/app/controllers/hourglass/api_base_controller.rb
@@ -14,6 +14,7 @@ class ApiBaseController < ApplicationController
     include ::AuthorizationConcern
 
     private
+
     # use only these codes:
     # :ok (200)
     # :not_modified (304)
@@ -24,8 +25,8 @@ class ApiBaseController < ApplicationController
     # :internal_server_error (500)
     def respond_with_error(status, message, **options)
       render json: {
-          message: message.is_a?(Array) && options[:array_mode] == :sentence ? message.to_sentence : message,
-          status: Rack::Utils.status_code(status)
+        message: message.is_a?(Array) && options[:array_mode] == :sentence ? message.to_sentence : message,
+        status: Rack::Utils.status_code(status)
       },
              status: status
       throw :halt unless options[:no_halt]
@@ -71,18 +72,25 @@ def list_records(klass)
       scope = @query.results_scope order: sort_clause
       offset, limit = api_offset_and_limit
       respond_with_success(
-          count: scope.count,
-          offset: offset,
-          limit: limit,
-          records: scope.offset(offset).limit(limit).to_a
+        count: scope.count,
+        offset: offset,
+        limit: limit,
+        records: scope.offset(offset).limit(limit).to_a
       )
     end
 
     def bulk(params_key = controller_name, &block)
       @bulk_success = []
       @bulk_errors = []
-      params[params_key].each_with_index do |(id, params), index|
-        id, params = "new#{index}", id if id.is_a?(Hash)
+      entries = params[params_key]
+      entries = entries.to_unsafe_h if Rails::VERSION::MAJOR >= 5 && entries.instance_of?(ActionController::Parameters)
+      entries.each_with_index do |(id, params), index|
+        if Rails::VERSION::MAJOR <= 4
+          id, params = "new#{index}", id if id.is_a?(Hash)
+        else
+          id, params = "new#{index}", id if id.instance_of?(ActionController::Parameters)
+          params = ActionController::Parameters.new(params) if params.is_a?(Hash)
+        end
         error_preface = id.start_with?('new') ? bulk_error_preface(index, mode: :create) : bulk_error_preface(id)
         evaluate_entry bulk_entry(id, params, &block), error_preface
       end
@@ -132,7 +140,7 @@ def internal_server_error(e)
     end
 
     def flash_array(type, messages)
-      flash[type] = render_to_string partial: 'hourglass_ui/flash_array', locals: {messages: messages}
+      flash[type] = render_to_string partial: 'hourglass_ui/flash_array', locals: { messages: messages }
     end
 
     def custom_field_keys(params_hash)
diff --git a/app/controllers/hourglass/time_logs_controller.rb b/app/controllers/hourglass/time_logs_controller.rb
index 329f12d0..c2ec9eef 100644
--- a/app/controllers/hourglass/time_logs_controller.rb
+++ b/app/controllers/hourglass/time_logs_controller.rb
@@ -107,6 +107,7 @@ def bulk_destroy
     end
 
     private
+
     def time_log_params(params_hash = params.require(:time_log))
       parse_boolean :round, params_hash.permit(:start, :stop, :comments, :round, :user_id)
     end
@@ -117,16 +118,16 @@ def create_time_log_params(params_hash = params.require(:time_log))
 
     def split_params
       parse_boolean [:round, :insert_new_before],
-                 {
-                     split_at: Time.parse(params[:split_at]),
-                     insert_new_before: params[:insert_new_before],
-                     round: params[:round]
-                 }
+                    {
+                      split_at: Time.parse(params[:split_at]),
+                      insert_new_before: params[:insert_new_before],
+                      round: params[:round]
+                    }
     end
 
     def time_booking_params(params_hash = params.require(:time_booking))
       parse_boolean :round, params_hash.permit(:comments, :project_id, :issue_id, :activity_id, :round,
-                                                      custom_field_values: custom_field_keys(params_hash))
+                                               custom_field_values: custom_field_keys(params_hash))
     end
 
     def time_log_from_id(id = params[:id])
diff --git a/app/models/concerns/hourglass/type_parsing.rb b/app/models/concerns/hourglass/type_parsing.rb
new file mode 100644
index 00000000..1d8b09d1
--- /dev/null
+++ b/app/models/concerns/hourglass/type_parsing.rb
@@ -0,0 +1,23 @@
+module Hourglass::TypeParsing
+  def parse_type(type, attribute)
+    if Rails::VERSION::MAJOR <= 4
+      case type
+      when :boolean
+        ActiveRecord::Type::Boolean.new.type_cast_from_user(attribute)
+      when :integer
+        ActiveRecord::Type::Integer.new.type_cast_from_user(attribute)
+      when :float
+        ActiveRecord::Type::Float.new.type_cast_from_user(attribute)
+      end
+    else
+      case type
+      when :boolean
+        ActiveRecord::Type::Boolean.new.cast(attribute)
+      when :integer
+        ActiveRecord::Type::Integer.new.cast(attribute)
+      when :float
+        ActiveRecord::Type::Float.new.cast(attribute)
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/app/models/hourglass/global_settings.rb b/app/models/hourglass/global_settings.rb
index e9072b6e..6bf5bfe4 100644
--- a/app/models/hourglass/global_settings.rb
+++ b/app/models/hourglass/global_settings.rb
@@ -1,5 +1,6 @@
 module Hourglass
   class GlobalSettings
+    include TypeParsing
     include ActiveModel::Model
 
     attr_accessor :round_sums_only,
@@ -14,8 +15,7 @@ class GlobalSettings
 
     validates :round_sums_only, inclusion: { in: ['true', 'false', '1', '0', true, false] }
     validates :round_minimum, numericality: { greater_than_or_equal_to: 0, less_than_or_equal_to: 24 }
-    validates :round_limit, numericality: { only_integer: true, greater_than_or_equal_to: 0,
-                                            less_than_or_equal_to: 100 }
+    validates :round_limit, numericality: { only_integer: true, greater_than_or_equal_to: 0, less_than_or_equal_to: 100 }
     validates :round_default, inclusion: { in: ['true', 'false', '1', '0', true, false] }
     validates :round_carry_over_due, numericality: { greater_than_or_equal_to: 0, less_than_or_equal_to: 24 }
     validates :report_title, length: { maximum: 23 }, presence: true
@@ -68,16 +68,5 @@ def resolve_types
       self.report_logo_width = parse_type :integer, @report_logo_width
       self.global_tracker = parse_type :boolean, @global_tracker
     end
-
-    def parse_type(type, attribute)
-      case type
-      when :boolean
-        ActiveRecord::Type::Boolean.new.type_cast_from_user(attribute)
-      when :integer
-        ActiveRecord::Type::Integer.new.type_cast_from_user(attribute)
-      when :float
-        ActiveRecord::Type::Float.new.type_cast_from_user(attribute)
-      end
-    end
   end
 end
diff --git a/app/models/hourglass/project_settings.rb b/app/models/hourglass/project_settings.rb
index f0934b58..bc59180a 100644
--- a/app/models/hourglass/project_settings.rb
+++ b/app/models/hourglass/project_settings.rb
@@ -1,5 +1,6 @@
 module Hourglass
   class ProjectSettings
+    include TypeParsing
     include ActiveModel::Model
 
     attr_accessor :round_sums_only,
@@ -9,13 +10,12 @@ class ProjectSettings
                   :round_carry_over_due
 
     validates :round_sums_only, inclusion: { in: ['true', 'false', true, false] }, allow_blank: true
-    validates :round_minimum, numericality: { greater_than_or_equal_to: 0, less_than_or_equal_to: 24 },
-                              allow_blank: true
+    validates :round_minimum, numericality: { greater_than_or_equal_to: 0, less_than_or_equal_to: 24 }, allow_blank: true
     validates :round_limit, numericality: { only_integer: true, greater_than_or_equal_to: 0,
                                             less_than_or_equal_to: 100 }, allow_blank: true
     validates :round_default, inclusion: { in: ['true', 'false', true, false] }, allow_blank: true
-    validates :round_carry_over_due, numericality: { greater_than_or_equal_to: 0, less_than_or_equal_to: 24 },
-                                     allow_blank: true
+    validates :round_carry_over_due, numericality: { greater_than_or_equal_to: 0,
+                                                     less_than_or_equal_to: 24 }, allow_blank: true
 
     def initialize(project = nil)
       @project = project
@@ -36,6 +36,7 @@ def update(attributes)
     end
 
     private
+
     def from_hash(attributes)
       self.round_sums_only = attributes[:round_sums_only]
       self.round_minimum = attributes[:round_minimum]
@@ -61,16 +62,5 @@ def resolve_types
       self.round_default = parse_type :boolean, @round_default
       self.round_carry_over_due = parse_type :float, @round_carry_over_due
     end
-
-    def parse_type(type, attribute)
-      case type
-      when :boolean
-        ActiveRecord::Type::Boolean.new.type_cast_from_user(attribute)
-      when :integer
-        ActiveRecord::Type::Integer.new.type_cast_from_user(attribute)
-      when :float
-        ActiveRecord::Type::Float.new.type_cast_from_user(attribute)
-      end
-    end
   end
 end
diff --git a/app/views/hourglass_ui/forms/fields/_activity.slim b/app/views/hourglass_ui/forms/fields/_activity.slim
index bffcc788..b731bb77 100644
--- a/app/views/hourglass_ui/forms/fields/_activity.slim
+++ b/app/views/hourglass_ui/forms/fields/_activity.slim
@@ -2,4 +2,4 @@
   .label
     = form.label :activity_id
   .input
-    = form.collection_select :activity_id, TimeEntryActivity.applicable(entry.project), :id, :name, {include_blank: !local_assigns[:required]}, disabled: local_assigns[:disabled], required: local_assigns[:required]
+    = form.collection_select :activity_id, TimeEntryActivity.applicable(entry.project), :id, :name, { include_blank: true }, disabled: local_assigns[:disabled], required: local_assigns[:required]
diff --git a/app/views/hourglass_ui/forms/fields/_project.slim b/app/views/hourglass_ui/forms/fields/_project.slim
index 6af5e777..3da40bd2 100644
--- a/app/views/hourglass_ui/forms/fields/_project.slim
+++ b/app/views/hourglass_ui/forms/fields/_project.slim
@@ -4,4 +4,4 @@
     - if local_assigns[:with_link]
       = link_to '', project_path(id: entry.project_id || ''), class: css_classes('icon icon-link', ('hidden' unless entry.project))
   .input
-    = form.select :project_id, projects_for_project_select(entry.project), {include_blank: !local_assigns[:required]}, disabled: local_assigns[:disabled], required: local_assigns[:required]
+    = form.select :project_id, projects_for_project_select(entry.project), { include_blank: true }, disabled: local_assigns[:disabled], required: local_assigns[:required]
diff --git a/app/views/hourglass_ui/forms/fields/_user_id.slim b/app/views/hourglass_ui/forms/fields/_user_id.slim
index 27fadb1c..569b1cbc 100644
--- a/app/views/hourglass_ui/forms/fields/_user_id.slim
+++ b/app/views/hourglass_ui/forms/fields/_user_id.slim
@@ -3,4 +3,4 @@
     = form.label :user_id
   .input
     - project = entry && entry.respond_to?(:project) && entry.project || nil
-    = form.select :user_id, options_from_collection_for_select(user_collection(project), :id, :name, entry.user_id || User.current.id), {include_blank: !local_assigns[:required]}, disabled: local_assigns[:disabled], required: local_assigns[:required]
+    = form.select :user_id, options_from_collection_for_select(user_collection(project), :id, :name, entry.user_id || User.current.id), { include_blank: true }, disabled: local_assigns[:disabled], required: local_assigns[:required]
diff --git a/app/views/hourglass_ui/time_bookings/context_menu.slim b/app/views/hourglass_ui/time_bookings/context_menu.slim
index bbc8be85..f7074692 100644
--- a/app/views/hourglass_ui/time_bookings/context_menu.slim
+++ b/app/views/hourglass_ui/time_bookings/context_menu.slim
@@ -1,6 +1,6 @@
 - ids = @records.map(&:id)
 ul
-  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_bookings_path(ids: ids), class: 'icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_booking| policy(time_booking).change? }
-  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_booking_path(@records.first) : bulk_destroy_hourglass_time_bookings_path(time_bookings: ids), class: 'icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_booking| policy(time_booking).destroy? }
+  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_bookings_path(ids: ids), class: 'icon icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_booking| policy(time_booking).change? }
+  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_booking_path(@records.first) : bulk_destroy_hourglass_time_bookings_path(time_bookings: ids), class: 'icon icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_booking| policy(time_booking).destroy? }
 
 
diff --git a/app/views/hourglass_ui/time_logs/context_menu.slim b/app/views/hourglass_ui/time_logs/context_menu.slim
index a23ab536..0a7d3188 100644
--- a/app/views/hourglass_ui/time_logs/context_menu.slim
+++ b/app/views/hourglass_ui/time_logs/context_menu.slim
@@ -1,8 +1,8 @@
 - ids = @records.map(&:id)
 ul
-  li = context_menu_link t('hourglass.ui.lists.button_book'), hourglass_ui_bulk_book_time_logs_path(ids: ids), class: 'icon-time js-show-inline-form-multi', title: t('hourglass.ui.lists.button_book'), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_log| policy(time_log).book? }
-  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_logs_path(ids: ids), class: 'icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_log| policy(time_log).change? }
-  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_log_path(@records.first) : bulk_destroy_hourglass_time_logs_path(time_logs: ids), class: 'icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_log| policy(time_log).destroy? }
-  li = context_menu_link t('hourglass.ui.time_logs.button_join'), join_hourglass_time_logs_path(ids: ids), class: 'icon-hourglass-join js-hourglass-remote', title: t('hourglass.ui.time_logs.button_join'), remote: true, data: {method: 'post'}, disabled: ids.length == 1 || !@records.all? { |time_log| policy(time_log).join? } && Hourglass::TimeLog.joinable?(*ids)
+  li = context_menu_link t('hourglass.ui.lists.button_book'), hourglass_ui_bulk_book_time_logs_path(ids: ids), class: 'icon icon-time js-show-inline-form-multi', title: t('hourglass.ui.lists.button_book'), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_log| policy(time_log).book? }
+  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_logs_path(ids: ids), class: 'icon icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_log| policy(time_log).change? }
+  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_log_path(@records.first) : bulk_destroy_hourglass_time_logs_path(time_logs: ids), class: 'icon icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_log| policy(time_log).destroy? }
+  li = context_menu_link t('hourglass.ui.time_logs.button_join'), join_hourglass_time_logs_path(ids: ids), class: 'icon icon-hourglass-join js-hourglass-remote', title: t('hourglass.ui.time_logs.button_join'), remote: true, data: {method: 'post'}, disabled: ids.length == 1 || !@records.all? { |time_log| policy(time_log).join? } && Hourglass::TimeLog.joinable?(*ids)
   - time_bookings = @records.map(&:time_booking).compact
-  li = context_menu_link t('hourglass.ui.lists.button_delete_booking'), time_bookings.length == 1 ? hourglass_time_booking_path(time_bookings.first) : bulk_destroy_hourglass_time_bookings_path(time_bookings: time_bookings.map(&:id)), class: 'icon-del js-hourglass-remote', title: t('hourglass.ui.lists.button_delete_booking'), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !time_bookings.present? || !time_bookings.all? { |time_booking| policy(time_booking).destroy? }
+  li = context_menu_link t('hourglass.ui.lists.button_delete_booking'), time_bookings.length == 1 ? hourglass_time_booking_path(time_bookings.first) : bulk_destroy_hourglass_time_bookings_path(time_bookings: time_bookings.map(&:id)), class: 'icon icon-del js-hourglass-remote', title: t('hourglass.ui.lists.button_delete_booking'), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !time_bookings.present? || !time_bookings.all? { |time_booking| policy(time_booking).destroy? }
diff --git a/app/views/hourglass_ui/time_trackers/context_menu.slim b/app/views/hourglass_ui/time_trackers/context_menu.slim
index 1bc9fe30..9db28d6f 100644
--- a/app/views/hourglass_ui/time_trackers/context_menu.slim
+++ b/app/views/hourglass_ui/time_trackers/context_menu.slim
@@ -1,4 +1,4 @@
 - ids = @records.map(&:id)
 ul
-  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_trackers_path(ids: ids), class: 'icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_tracker| policy(time_tracker).change? }
-  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_tracker_path(@records.first) : bulk_destroy_hourglass_time_trackers_path(time_trackers: ids), class: 'icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_tracker| policy(time_tracker).destroy? }
+  li = context_menu_link t(:button_edit), hourglass_ui_bulk_edit_time_trackers_path(ids: ids), class: 'icon icon-edit js-show-inline-form-multi', title: t(:button_edit), remote: true, data: {type: 'html'}, disabled: !@records.all? { |time_tracker| policy(time_tracker).change? }
+  li = context_menu_link t(:button_delete), @records.length == 1 ? hourglass_time_tracker_path(@records.first) : bulk_destroy_hourglass_time_trackers_path(time_trackers: ids), class: 'icon icon-del js-hourglass-remote', title: t(:button_delete), remote: true, method: :delete, data: {confirm: t(:text_are_you_sure)}, disabled: !@records.all? { |time_tracker| policy(time_tracker).destroy? }
diff --git a/config/initializers/autoload.rb b/config/initializers/autoload.rb
index 6911ff2f..e73ebf10 100644
--- a/config/initializers/autoload.rb
+++ b/config/initializers/autoload.rb
@@ -1,8 +1,8 @@
 [
-    %w(app models concerns),
-    %w(app controllers concerns),
-    %w(app policies),
-    %w(app policies concerns)
+  %w(app models concerns),
+  %w(app controllers concerns),
+  %w(app policies),
+  %w(app policies concerns)
 ].each do |path|
   ActiveSupport::Dependencies.autoload_paths << File.join(Hourglass::PLUGIN_ROOT, *path)
 end
diff --git a/config/initializers/redmine_integration.rb b/config/initializers/redmine_integration.rb
index 5033cefc..3bd29dcd 100644
--- a/config/initializers/redmine_integration.rb
+++ b/config/initializers/redmine_integration.rb
@@ -3,7 +3,11 @@ def add_patch(module_to_patch, method: :include)
   module_to_patch.send method, patch unless module_to_patch.ancestors.include? patch
 end
 
-ActionDispatch::Callbacks.to_prepare do
+if Rails::VERSION::MAJOR >= 5
+  ActiveSupport::Reloader
+else
+  ActionDispatch::Callbacks
+end.to_prepare do
   [Project, TimeEntry, User, ProjectsHelper, SettingsController, UserPreference, TimeEntryActivity].each { |module_to_patch| add_patch module_to_patch }
   [Query].each { |module_to_patch| add_patch module_to_patch, method: :prepend }
 
diff --git a/db/migrate/1418311263_create_hourglass_time_logs.rb b/db/migrate/1418311263_create_hourglass_time_logs.rb
index 870ae6ab..39882bca 100644
--- a/db/migrate/1418311263_create_hourglass_time_logs.rb
+++ b/db/migrate/1418311263_create_hourglass_time_logs.rb
@@ -1,4 +1,6 @@
-class CreateHourglassTimeLogs < ActiveRecord::Migration
+require 'hourglass/hourglass_migration'
+
+class CreateHourglassTimeLogs < HourglassMigration
   def change
     create_table :hourglass_time_logs do |t|
       t.datetime :start, null: false
diff --git a/db/migrate/1418311331_create_hourglass_time_bookings.rb b/db/migrate/1418311331_create_hourglass_time_bookings.rb
index dd57d69d..ba7a5d58 100644
--- a/db/migrate/1418311331_create_hourglass_time_bookings.rb
+++ b/db/migrate/1418311331_create_hourglass_time_bookings.rb
@@ -1,4 +1,6 @@
-class CreateHourglassTimeBookings < ActiveRecord::Migration
+require 'hourglass/hourglass_migration'
+
+class CreateHourglassTimeBookings < HourglassMigration
   def change
     create_table :hourglass_time_bookings do |t|
       t.datetime :start, null: false
diff --git a/db/migrate/1418914331_create_hourglass_time_trackers.rb b/db/migrate/1418914331_create_hourglass_time_trackers.rb
index a81b3326..522a9d4d 100644
--- a/db/migrate/1418914331_create_hourglass_time_trackers.rb
+++ b/db/migrate/1418914331_create_hourglass_time_trackers.rb
@@ -1,4 +1,6 @@
-class CreateHourglassTimeTrackers < ActiveRecord::Migration
+require 'hourglass/hourglass_migration'
+
+class CreateHourglassTimeTrackers < HourglassMigration
   def change
     create_table :hourglass_time_trackers do |t|
       t.datetime :start, null: false
diff --git a/db/migrate/20190307074023_change_hourglass_time_log_comments_limit.rb b/db/migrate/20190307074023_change_hourglass_time_log_comments_limit.rb
index dfe65687..e61427b9 100644
--- a/db/migrate/20190307074023_change_hourglass_time_log_comments_limit.rb
+++ b/db/migrate/20190307074023_change_hourglass_time_log_comments_limit.rb
@@ -1,4 +1,6 @@
-class ChangeHourglassTimeLogCommentsLimit < ActiveRecord::Migration
+require 'hourglass/hourglass_migration'
+
+class ChangeHourglassTimeLogCommentsLimit < HourglassMigration
   def up
     change_column :hourglass_time_logs, :comments, :string, limit: 1024
   end
diff --git a/lib/hourglass/hourglass_migration.rb b/lib/hourglass/hourglass_migration.rb
new file mode 100644
index 00000000..6d6d0ba1
--- /dev/null
+++ b/lib/hourglass/hourglass_migration.rb
@@ -0,0 +1,2 @@
+class HourglassMigration < (Rails::VERSION::MAJOR <= 4 ? ActiveRecord::Migration : ActiveRecord::Migration[4.2])
+end
diff --git a/lib/hourglass/redmine_patches/projects_helper_patch.rb b/lib/hourglass/redmine_patches/projects_helper_patch.rb
index 75c8dbb8..7b12b579 100644
--- a/lib/hourglass/redmine_patches/projects_helper_patch.rb
+++ b/lib/hourglass/redmine_patches/projects_helper_patch.rb
@@ -4,7 +4,8 @@ module ProjectsHelperPatch
       extend ActiveSupport::Concern
 
       included do
-        alias_method_chain :project_settings_tabs, :hourglass
+        alias_method :project_settings_tabs_without_hourglass, :project_settings_tabs
+        alias_method :project_settings_tabs, :project_settings_tabs_with_hourglass
       end
 
       def project_settings_tabs_with_hourglass
diff --git a/lib/hourglass/redmine_patches/settings_controller_patch.rb b/lib/hourglass/redmine_patches/settings_controller_patch.rb
index e38da7e6..7495fec0 100644
--- a/lib/hourglass/redmine_patches/settings_controller_patch.rb
+++ b/lib/hourglass/redmine_patches/settings_controller_patch.rb
@@ -4,7 +4,8 @@ module SettingsControllerPatch
       extend ActiveSupport::Concern
 
       included do
-        alias_method_chain :plugin, :hourglass
+        alias_method :plugin_without_hourglass, :plugin
+        alias_method :plugin, :plugin_with_hourglass
       end
 
       def plugin_with_hourglass
diff --git a/spec/integration/time_bookings_spec.rb b/spec/integration/time_bookings_spec.rb
index 8d7cc855..c773d2a2 100644
--- a/spec/integration/time_bookings_spec.rb
+++ b/spec/integration/time_bookings_spec.rb
@@ -90,7 +90,7 @@
       tags 'Time bookings'
       parameter name: :id, in: :path, type: :string
       parameter name: :time_booking, in: :body, schema: {
-          '$ref' => '#/definitions/time_booking_params'
+        '$ref' => '#/definitions/time_booking_params'
       }
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_booked_time, :hourglass_view_booked_time] }
@@ -98,7 +98,7 @@
         time_booking = create :time_booking, project: user.projects.first, user: user
         time_booking.id
       end
-      let(:time_booking) { {time_booking: {comments: 'test2'}} }
+      let(:time_booking) { { time_booking: { comments: 'test2' } } }
 
       include_examples 'access rights', :hourglass_book_time, :hourglass_book_own_time, :hourglass_edit_booked_time, :hourglass_edit_own_booked_time, success_code: '204'
 
@@ -107,7 +107,7 @@
         let(:time_booking) do
           project = create :project
           create :member, project: project, user: user, permissions: [:hourglass_edit_booked_time, :hourglass_view_booked_time]
-          {time_booking: {project_id: project.id}}
+          { time_booking: { project_id: project.id } }
         end
         response '204', 'time booking found' do
           run_test!
@@ -123,7 +123,7 @@
   path '/time_bookings/bulk_destroy.json' do
     delete 'Deletes multiple time bookings at once' do
       tags 'Time bookings'
-      parameter name: :'time_bookings[]', in: :query, type: :array, items: {type: :string}, collectionFormat: :multi
+      parameter name: :'time_bookings[]', in: :query, type: :array, items: { type: :string }, collectionFormat: :multi
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_booked_time, :hourglass_view_booked_time] }
       let(:time_booking_ids) do
@@ -147,7 +147,7 @@
       consumes 'application/json'
       produces 'application/json'
       tags 'Time bookings'
-      parameter name: :time_bookings, in: :body, schema: {type: :object, additionalProperties: {'$ref' => '#/definitions/time_booking'}}, description: 'takes an object of time bookings'
+      parameter name: :time_bookings, in: :body, schema: { type: :object, additionalProperties: { '$ref' => '#/definitions/time_booking' } }, description: 'takes an object of time bookings'
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_booked_time, :hourglass_view_booked_time] }
       let(:time_booking_ids) do
@@ -156,7 +156,7 @@
         [tt1.id, tt2.id]
       end
 
-      let(:time_bookings) { {time_bookings: {time_booking_ids[0] => {comments: 'test3'}, time_booking_ids[1] => {comments: 'test4'}}} }
+      let(:time_bookings) { { time_bookings: { time_booking_ids[0] => { comments: 'test3' }, time_booking_ids[1] => { comments: 'test4' } } } }
 
       include_examples 'access rights', :hourglass_book_time, :hourglass_book_own_time, :hourglass_edit_booked_time, :hourglass_edit_own_booked_time
 
@@ -176,17 +176,17 @@
       consumes 'application/json'
       produces 'application/json'
       tags 'Time bookings'
-      parameter name: :time_bookings, in: :body, schema: {type: :array, items: {'$ref' => '#/definitions/time_booking'}}, description: 'takes an array of time bookings'
+      parameter name: :time_bookings, in: :body, schema: { type: :array, items: { '$ref' => '#/definitions/time_booking' } }, description: 'takes an array of time bookings'
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_booked_time] }
 
       let(:time_bookings) do
         {
-            time_bookings: [
-                {user_id: user.id, project_id: user.projects.first.id, activity_id: create(:time_entry_activity).id,
-                 start: Faker::Time.between(Date.today, Date.today, :morning),
-                 stop: Faker::Time.between(Date.today, Date.today, :afternoon)}
-            ]
+          time_bookings: [
+            { user_id: user.id, project_id: user.projects.first.id, activity_id: create(:time_entry_activity).id,
+              start: Faker::Time.between(Date.today, Date.today, :morning),
+              stop: Faker::Time.between(Date.today, Date.today, :afternoon) }
+          ]
         }
       end
 
@@ -197,17 +197,17 @@
           activity = create :time_entry_activity
           project = user.projects.first
           {
-              time_bookings: [
-                  {user_id: user.id, project_id: project.id, activity_id: activity.id,
-                   start: Faker::Time.between(Date.today, Date.today, :morning),
-                   stop: Faker::Time.between(Date.today, Date.today, :afternoon)},
-                  {user_id: create(:user).id, project_id: project.id, activity_id: activity.id,
-                   start: Faker::Time.between(Date.today, Date.today, :morning),
-                   stop: Faker::Time.between(Date.today, Date.today, :afternoon)},
-                  {user_id: create(:user).id, project_id: project.id, activity_id: activity.id,
-                   start: Faker::Time.between(Date.today, Date.today, :morning),
-                   stop: Faker::Time.between(Date.today, Date.today, :afternoon)}
-              ]
+            time_bookings: [
+              { user_id: user.id, project_id: project.id, activity_id: activity.id,
+                start: Faker::Time.between(Date.today, Date.today, :morning),
+                stop: Faker::Time.between(Date.today, Date.today, :afternoon) },
+              { user_id: create(:user).id, project_id: project.id, activity_id: activity.id,
+                start: Faker::Time.between(Date.today, Date.today, :morning),
+                stop: Faker::Time.between(Date.today, Date.today, :afternoon) },
+              { user_id: create(:user).id, project_id: project.id, activity_id: activity.id,
+                start: Faker::Time.between(Date.today, Date.today, :morning),
+                stop: Faker::Time.between(Date.today, Date.today, :afternoon) }
+            ]
           }
         end
         run_test!
diff --git a/spec/integration/time_logs_spec.rb b/spec/integration/time_logs_spec.rb
index ed14dfe8..ebb66ed3 100644
--- a/spec/integration/time_logs_spec.rb
+++ b/spec/integration/time_logs_spec.rb
@@ -89,19 +89,19 @@
       tags 'Time logs'
       parameter name: :id, in: :path, type: :string
       parameter name: :time_log, in: :body, schema: {
-          '$ref' => '#/definitions/time_log_update'
+        '$ref' => '#/definitions/time_log_update'
       }
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_tracked_time] }
       let(:existing_time_log) { create :time_log, user: user }
       let(:id) { existing_time_log.id }
-      let(:time_log) { {time_log: {comments: 'test2'}} }
+      let(:time_log) { { time_log: { comments: 'test2' } } }
 
       include_examples 'access rights', :hourglass_track_time, :hourglass_edit_tracked_time, :hourglass_edit_own_tracked_time, success_code: '204'
 
       include_examples 'not found'
       context do
-        let(:time_log) { {time_log: {stop: existing_time_log.stop + 1.hour}} }
+        let(:time_log) { { time_log: { stop: existing_time_log.stop + 1.hour } } }
         response '204', 'time log found' do
           run_test!
 
@@ -120,15 +120,15 @@
       tags 'Time logs'
       parameter name: :id, in: :path, type: :string
       parameter name: :time_booking, in: :body, schema: {
-          '$ref' => '#/definitions/time_booking_params'
+        '$ref' => '#/definitions/time_booking_params'
       }
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_book_time] }
       let(:time_log) { create :time_log, user: user }
       let(:id) { time_log.id }
-      let(:time_booking) { {time_booking: {
-          project_id: user.projects.first.id, activity_id: create(:time_entry_activity).id
-      }} }
+      let(:time_booking) { { time_booking: {
+        project_id: user.projects.first.id, activity_id: create(:time_entry_activity).id
+      } } }
 
       include_examples 'access rights', :hourglass_book_time, :hourglass_book_own_time
       include_examples 'not found'
@@ -169,14 +169,14 @@
       response '200', 'time log found' do
         schema type: 'object',
                properties: {
-                   time_log: {
-                       '$ref' => '#/definitions/time_log',
-                       required: %w(id start stop user_id created_at updated_at)
-                   },
-                   new_time_log: {
-                       '$ref' => '#/definitions/time_log',
-                       required: %w(id start stop user_id created_at updated_at)
-                   }
+                 time_log: {
+                   '$ref' => '#/definitions/time_log',
+                   required: %w(id start stop user_id created_at updated_at)
+                 },
+                 new_time_log: {
+                   '$ref' => '#/definitions/time_log',
+                   required: %w(id start stop user_id created_at updated_at)
+                 }
                }
 
         include_examples 'has a valid response'
@@ -195,7 +195,7 @@
     post 'Joins multiple time logs' do
       produces 'application/json'
       tags 'Time logs'
-      parameter name: :'ids[]', in: :query, type: :array, items: {type: :integer}, collectionFormat: :multi
+      parameter name: :'ids[]', in: :query, type: :array, items: { type: :integer }, collectionFormat: :multi
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_track_time] }
       let(:time_log) { create :time_log, user: user }
@@ -211,10 +211,10 @@
       response '200', 'time logs found' do
         schema type: 'object',
                properties: {
-                   time_log: {
-                       '$ref' => '#/definitions/time_log',
-                       required: %w(id start stop user_id created_at updated_at)
-                   }
+                 time_log: {
+                   '$ref' => '#/definitions/time_log',
+                   required: %w(id start stop user_id created_at updated_at)
+                 }
                }
 
         include_examples 'has a valid response'
@@ -236,7 +236,7 @@
   path '/time_logs/bulk_destroy.json' do
     delete 'Deletes multiple time logs at once' do
       tags 'Time logs'
-      parameter name: :'time_logs[]', in: :query, type: :array, items: {type: :string}, collectionFormat: :multi
+      parameter name: :'time_logs[]', in: :query, type: :array, items: { type: :string }, collectionFormat: :multi
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_tracked_time] }
       let(:time_log_ids) do
@@ -260,7 +260,7 @@
       consumes 'application/json'
       produces 'application/json'
       tags 'Time logs'
-      parameter name: :time_logs, in: :body, schema: {type: :object, additionalProperties: {'$ref' => '#/definitions/time_log'}}, description: 'takes an object of time logs'
+      parameter name: :time_logs, in: :body, schema: { type: :object, additionalProperties: { '$ref' => '#/definitions/time_log' } }, description: 'takes an object of time logs'
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_tracked_time, :hourglass_view_tracked_time] }
       let(:time_log_ids) do
@@ -269,7 +269,7 @@
         [tt1.id, tt2.id]
       end
 
-      let(:time_logs) { {time_logs: {time_log_ids[0] => {comments: 'test3'}, time_log_ids[1] => {comments: 'test4'}}} }
+      let(:time_logs) { { time_logs: { time_log_ids[0] => { comments: 'test3' }, time_log_ids[1] => { comments: 'test4' } } } }
 
       include_examples 'access rights', :hourglass_track_time, :hourglass_edit_tracked_time, :hourglass_edit_own_tracked_time
 
@@ -289,7 +289,7 @@
       consumes 'application/json'
       produces 'application/json'
       tags 'Time logs'
-      parameter name: :time_bookings, in: :body, schema: {type: :object, additionalProperties: {'$ref' => '#/definitions/time_booking'}}, description: 'takes an object of time bookings'
+      parameter name: :time_bookings, in: :body, schema: { type: :object, additionalProperties: { '$ref' => '#/definitions/time_booking' } }, description: 'takes an object of time bookings'
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_book_time, :hourglass_view_tracked_time] }
       let(:time_logs) do
@@ -300,9 +300,9 @@
 
       let(:time_bookings) do
         tl1, tl2 = time_logs
-        {time_bookings: {
-            tl1.id => {project_id: tl1.user.projects.first.id, activity_id: create(:time_entry_activity).id},
-            tl2.id => {}
+        { time_bookings: {
+          tl1.id => { project_id: tl1.user.projects.first.id, activity_id: create(:time_entry_activity).id },
+          tl2.id => {}
         }
         }
       end
@@ -324,15 +324,15 @@
       consumes 'application/json'
       produces 'application/json'
       tags 'Time logs'
-      parameter name: :time_logs, in: :body, schema: {type: :array, items: {'$ref' => '#/definitions/time_log'}}, description: 'takes an array of time logs'
+      parameter name: :time_logs, in: :body, schema: { type: :array, items: { '$ref' => '#/definitions/time_log' } }, description: 'takes an array of time logs'
 
       let(:user) { create :user, :as_member, permissions: [:hourglass_edit_tracked_time] }
 
       let(:time_logs) do
-        {time_logs: [
-            build(:time_log, user: user),
-            build(:time_log),
-            build(:time_log)
+        { time_logs: [
+          build(:time_log, user: user),
+          build(:time_log),
+          build(:time_log)
         ]
         }
       end