diff --git a/acts_as_nested_interval.gemspec b/acts_as_nested_interval.gemspec
index e1b6176..5368ec1 100644
--- a/acts_as_nested_interval.gemspec
+++ b/acts_as_nested_interval.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*"] + ["MIT-LICENSE", "Rakefile", "README.md"]
   s.test_files = Dir["test/**/*"]
 
-  s.add_dependency "rails", "~> 3.2.1"
+  s.add_dependency "rails", ">= 3.2.1", "< 5"
 
   s.add_development_dependency "sqlite3"
   s.add_development_dependency "mysql2"
diff --git a/lib/acts_as_nested_interval.rb b/lib/acts_as_nested_interval.rb
index 6debd23..13dfb10 100644
--- a/lib/acts_as_nested_interval.rb
+++ b/lib/acts_as_nested_interval.rb
@@ -37,14 +37,14 @@ def acts_as_nested_interval(options = {})
     belongs_to :parent, class_name: name, foreign_key: nested_interval_foreign_key
     has_many :children, class_name: name, foreign_key: nested_interval_foreign_key,
       dependent: nested_interval_dependent
-    scope :roots, where(nested_interval_foreign_key => nil)
+    scope :roots, -> { where(nested_interval_foreign_key => nil) }
       
     if columns_hash["rgt"]
-      scope :preorder, order('rgt DESC, lftp ASC')
+      scope :preorder, -> { order('rgt DESC, lftp ASC') }
     elsif columns_hash["rgtp"] && columns_hash["rgtq"]
-      scope :preorder, order('1.0 * rgtp / rgtq DESC, lftp ASC')
+      scope :preorder, -> { order('1.0 * rgtp / rgtq DESC, lftp ASC') }
     else
-      scope :preorder, order('nested_interval_rgt(lftp, lftq) DESC, lftp ASC')
+      scope :preorder, -> { order('nested_interval_rgt(lftp, lftq) DESC, lftp ASC') }
     end
 
     before_create :create_nested_interval