diff --git a/.rubocop.yml b/.rubocop.yml
index be830179..9842cee1 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -20,7 +20,7 @@ Metrics/BlockLength:
 Metrics/ClassLength:
   Max: 250
 Metrics/LineLength:
-  Max: 100
+  Max: 128
 Style/Documentation:
   Enabled: false
 Style/ModuleFunction:
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 4abdbce5..c7549a8b 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2020-06-22 23:35:07 +0800 using RuboCop version 0.82.0.
+# on 2020-06-29 08:44:31 -0400 using RuboCop version 0.82.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -30,7 +30,7 @@ Lint/SuppressedException:
 Metrics/AbcSize:
   Max: 39
 
-# Offense count: 1
+# Offense count: 2
 # Configuration parameters: IgnoredMethods.
 Metrics/CyclomaticComplexity:
   Max: 9
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8ee641c..5bcf9f9a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 * [#324](https://github.com/slack-ruby/slack-ruby-client/pull/324): Upgrade slack-ruby-danger, rubocop, rubocop-rspec and rubocop-performance - [@dblock](https://github.com/dblock).
 * [#327](https://github.com/slack-ruby/slack-ruby-client/pull/327), [#326](https://github.com/slack-ruby/slack-ruby-client/pull/326): Added `admin_conversations_whitelist`, `admin_usergroups`, `calls` and `calls_participants` endpoints  - [@wasabigeek](https://github.com/wasabigeek).
 * [#329](https://github.com/slack-ruby/slack-ruby-client/pull/329): Log when methods are deprecated - [@wasabigeek](https://github.com/wasabigeek).
+* [#325](https://github.com/slack-ruby/slack-ruby-client/pull/325): Remove activesupport dependency - [@ianks](https://github.com/ianks).
 * Your contribution here.
 
 ### 0.14.6 (2020/3/28)
diff --git a/UPGRADING.md b/UPGRADING.md
index ab538662..bcc0e03a 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -1,6 +1,12 @@
 Upgrading Slack-Ruby-Client
 ===========================
 
+### Upgrading to >= 0.15.0
+
+As of 0.15.0, `activesupport` is no longer required. Add `gem 'activesupport'` to your Gemfile if you required ActiveSupport via this library.
+
+See [#325](https://github.com/slack-ruby/slack-ruby-client/pull/325) for more information.
+
 ### Upgrading to >= 0.14.0
 
 If you are using async-websocket, lock down its version to 0.8.0 as newer versions are currently incompatible.
diff --git a/lib/slack-ruby-client.rb b/lib/slack-ruby-client.rb
index a4fe898b..81848117 100644
--- a/lib/slack-ruby-client.rb
+++ b/lib/slack-ruby-client.rb
@@ -37,8 +37,6 @@
 require_relative 'slack/web/client'
 
 # RealTime API
-require 'active_support'
-require 'active_support/core_ext'
 require_relative 'slack/real_time/concurrency'
 require_relative 'slack/real_time/socket'
 require_relative 'slack/real_time/api/message_id'
diff --git a/lib/slack/messages/message.rb b/lib/slack/messages/message.rb
index 54492367..b47d6d40 100644
--- a/lib/slack/messages/message.rb
+++ b/lib/slack/messages/message.rb
@@ -2,10 +2,6 @@
 module Slack
   module Messages
     class Message < Hashie::Mash
-      def presence
-        super['presence']
-      end
-
       def to_s
         keys.sort_by(&:to_s).map do |key|
           "#{key}=#{self[key]}"
diff --git a/lib/slack/real_time/concurrency/async.rb b/lib/slack/real_time/concurrency/async.rb
index b206bf30..437e04df 100644
--- a/lib/slack/real_time/concurrency/async.rb
+++ b/lib/slack/real_time/concurrency/async.rb
@@ -114,9 +114,7 @@ def build_ssl_context
 
           def build_endpoint
             endpoint = ::Async::IO::Endpoint.tcp(addr, port)
-            if secure?
-              endpoint = ::Async::IO::SSLEndpoint.new(endpoint, ssl_context: build_ssl_context)
-            end
+            endpoint = ::Async::IO::SSLEndpoint.new(endpoint, ssl_context: build_ssl_context) if secure?
             endpoint
           end
 
diff --git a/lib/slack/real_time/concurrency/eventmachine.rb b/lib/slack/real_time/concurrency/eventmachine.rb
index 9820d721..4249df88 100644
--- a/lib/slack/real_time/concurrency/eventmachine.rb
+++ b/lib/slack/real_time/concurrency/eventmachine.rb
@@ -8,9 +8,9 @@ module Concurrency
       module Eventmachine
         class Client < Faye::WebSocket::Client
           def initialize(url, protocols = nil, options = {})
-            @logger =
-              options.fetch(:logger) || Slack::RealTime::Config.logger || Slack::Config.logger
-            super url, protocols, options.except(:logger)
+            options = options.dup
+            @logger = options.delete(:logger) || Slack::RealTime::Config.logger || Slack::Config.logger
+            super url, protocols, options
           end
 
           def parse(data)
diff --git a/lib/slack/real_time/models/base.rb b/lib/slack/real_time/models/base.rb
index edb525ce..3d7d3447 100644
--- a/lib/slack/real_time/models/base.rb
+++ b/lib/slack/real_time/models/base.rb
@@ -3,10 +3,6 @@ module Slack
   module RealTime
     module Models
       class Base < Hashie::Mash
-        def presence
-          super['presence']
-        end
-
         # see https://github.com/intridea/hashie/issues/394
         def log_built_in_message(*); end
       end
diff --git a/lib/slack/real_time/socket.rb b/lib/slack/real_time/socket.rb
index 6870e87f..b5b701a1 100644
--- a/lib/slack/real_time/socket.rb
+++ b/lib/slack/real_time/socket.rb
@@ -8,9 +8,9 @@ class Socket
 
       def initialize(url, options = {})
         @url = url
-        @options = options
+        @options = options.dup
         @driver = nil
-        @logger = options.delete(:logger) || Slack::RealTime::Config.logger || Slack::Config.logger
+        @logger = @options.delete(:logger) || Slack::RealTime::Config.logger || Slack::Config.logger
         @last_message_at = nil
       end
 
diff --git a/lib/slack/real_time/stores/base.rb b/lib/slack/real_time/stores/base.rb
index 3a77fe38..484411c7 100644
--- a/lib/slack/real_time/stores/base.rb
+++ b/lib/slack/real_time/stores/base.rb
@@ -4,7 +4,9 @@ module RealTime
     module Stores
       # Doesn't store anything.
       class Base
-        class_attribute :events
+        class << self
+          attr_accessor :events
+        end
 
         attr_accessor :users
         attr_accessor :bots
diff --git a/lib/slack/web/api/mixins/ids.id.rb b/lib/slack/web/api/mixins/ids.id.rb
index 52261877..503ba50e 100644
--- a/lib/slack/web/api/mixins/ids.id.rb
+++ b/lib/slack/web/api/mixins/ids.id.rb
@@ -11,9 +11,7 @@ def id_for(key, name, prefix, list_method, not_found_error)
 
             yield.tap do |list|
               list.public_send(list_method).each do |li|
-                if li.name == name[1..-1]
-                  return Slack::Messages::Message.new('ok' => true, key.to_s => { 'id' => li.id })
-                end
+                return Slack::Messages::Message.new('ok' => true, key.to_s => { 'id' => li.id }) if li.name == name[1..-1]
               end
             end
 
diff --git a/lib/slack/web/pagination/cursor.rb b/lib/slack/web/pagination/cursor.rb
index 4446f9dc..e82458d8 100644
--- a/lib/slack/web/pagination/cursor.rb
+++ b/lib/slack/web/pagination/cursor.rb
@@ -32,14 +32,14 @@ def each
 
                 client.logger.debug("#{self.class}##{__method__}") { e.to_s }
                 retry_count += 1
-                sleep(e.retry_after.seconds)
+                sleep(e.retry_after)
                 next
               end
               yield response
               break unless response.response_metadata
 
               next_cursor = response.response_metadata.next_cursor
-              break if next_cursor.blank?
+              break if next_cursor.nil? || next_cursor == ''
 
               retry_count = 0
               sleep(sleep_interval) if sleep_interval
diff --git a/lib/tasks/web.rake b/lib/tasks/web.rake
index 618c7026..1e2fe632 100644
--- a/lib/tasks/web.rake
+++ b/lib/tasks/web.rake
@@ -2,8 +2,6 @@
 # largely from https://github.com/aki017/slack-ruby-gem
 require 'json-schema'
 require 'erubis'
-require 'active_support'
-require 'active_support/core_ext'
 
 namespace :slack do
   namespace :web do
diff --git a/slack-ruby-client.gemspec b/slack-ruby-client.gemspec
index ada9fd80..683236b5 100644
--- a/slack-ruby-client.gemspec
+++ b/slack-ruby-client.gemspec
@@ -17,12 +17,12 @@ Gem::Specification.new do |s|
   s.homepage = 'http://github.com/slack-ruby/slack-ruby-client'
   s.licenses = ['MIT']
   s.summary = 'Slack Web and RealTime API client.'
-  s.add_dependency 'activesupport'
   s.add_dependency 'faraday', '>= 1.0'
   s.add_dependency 'faraday_middleware'
   s.add_dependency 'gli'
   s.add_dependency 'hashie'
   s.add_dependency 'websocket-driver'
+  s.add_development_dependency 'activesupport'
   s.add_development_dependency 'erubis'
   s.add_development_dependency 'json-schema'
   s.add_development_dependency 'rake', '~> 10'