diff --git a/activerecord/lib/rails/generators/active_record/model/templates/module.rb b/activerecord/lib/rails/generators/active_record/model/templates/module.rb
index fca29080800f62c8b710d4421de22684c4f971d9..a3bf1c37b67b6a2e63e3c9ee57897ab75d34c287 100644
--- a/activerecord/lib/rails/generators/active_record/model/templates/module.rb
+++ b/activerecord/lib/rails/generators/active_record/model/templates/module.rb
@@ -1,7 +1,7 @@
 <% module_namespacing do -%>
 module <%= class_path.map(&:camelize).join('::') %>
   def self.table_name_prefix
-    '<%= class_path.join('_') %>_'
+    '<%= namespaced? ? namespaced_class_path.join('_') : class_path.join('_') %>_'
   end
 end
 <% end -%>
diff --git a/railties/test/generators/namespaced_generators_test.rb b/railties/test/generators/namespaced_generators_test.rb
index 2ae9dc61a74231e6efb01d9803f9c831c895d6a4..db2b8af217ed2b4b010f2777facc768c739e7f79 100644
--- a/railties/test/generators/namespaced_generators_test.rb
+++ b/railties/test/generators/namespaced_generators_test.rb
@@ -99,7 +99,7 @@ def test_model_with_namespace
     run_generator ["admin/account"]
     assert_file "app/models/test_app/admin.rb", /module TestApp/, /module Admin/
     assert_file "app/models/test_app/admin.rb", /def self\.table_name_prefix/
-    assert_file "app/models/test_app/admin.rb", /'admin_'/
+    assert_file "app/models/test_app/admin.rb", /'test_app_admin_'/
     assert_file "app/models/test_app/admin/account.rb", /module TestApp/, /class Admin::Account < ActiveRecord::Base/
   end