diff --git a/lib/kaminari/active_record_extension.rb b/lib/kaminari/active_record_extension.rb
index 08d2d84..eafdc80 100644
--- a/lib/kaminari/active_record_extension.rb
+++ b/lib/kaminari/active_record_extension.rb
@@ -1,7 +1,8 @@
 module Kaminari
+  DEFAULT_PER_PAGE = 25 unless defined? ::Kaminari::DEFAULT_PER_PAGE
+
   module ActiveRecordExtension
     extend ActiveSupport::Concern
-    DEFAULT_PER_PAGE = 25
 
     included do
       def self.inherited(kls) #:nodoc:
@@ -51,7 +52,7 @@ module Kaminari
           # This model's default per_page value
           # returns 25 unless explicitly overridden via <tt>paginates_per</tt>
           def self.default_per_page
-            @_default_per_page || Kaminari::ActiveRecordExtension::DEFAULT_PER_PAGE
+            @_default_per_page || Kaminari::DEFAULT_PER_PAGE
           end
         end
       end
diff --git a/lib/kaminari/mongoid_extension.rb b/lib/kaminari/mongoid_extension.rb
index a1b2828..27bd4b3 100644
--- a/lib/kaminari/mongoid_extension.rb
+++ b/lib/kaminari/mongoid_extension.rb
@@ -1,7 +1,7 @@
 module Kaminari
-  module MongoidExtension
-    DEFAULT_PER_PAGE = 25
+  DEFAULT_PER_PAGE = 25 unless defined? ::Kaminari::DEFAULT_PER_PAGE
 
+  module MongoidExtension
     module Criteria
       extend ActiveSupport::Concern
 
@@ -55,7 +55,7 @@ module Kaminari
         # This model's default per_page value
         # returns 25 unless explicitly overridden via <tt>paginates_per</tt>
         def self.default_per_page
-          @_default_per_page || Kaminari::MongoidExtension::DEFAULT_PER_PAGE
+          @_default_per_page || Kaminari::DEFAULT_PER_PAGE
         end
       end
     end