diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
index 1319fb2c83..7500eea492 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
@@ -62,11 +62,6 @@ Rails.application.configure do
 
   <%- end -%>
   <%- unless options.skip_sprockets? -%>
-  # Debug mode disables concatenation and preprocessing of assets.
-  # This option may cause significant delays in view rendering with a large
-  # number of complex assets.
-  config.assets.debug = true
-
   # Suppress logger output for asset requests.
   config.assets.quiet = true
   <%- end -%>
diff --git a/railties/test/application/assets_test.rb b/railties/test/application/assets_test.rb
index 95bdfd3238..8e9fb72538 100644
--- a/railties/test/application/assets_test.rb
+++ b/railties/test/application/assets_test.rb
@@ -472,9 +472,9 @@ module ApplicationTests
       class ::PostsController < ActionController::Base; end
 
       get "/posts", {}, { "HTTPS" => "off" }
-      assert_match('src="http://example.com/assets/application.debug.js', last_response.body)
+      assert_match('src="http://example.com/assets/application.js', last_response.body)
       get "/posts", {}, { "HTTPS" => "on" }
-      assert_match('src="https://example.com/assets/application.debug.js', last_response.body)
+      assert_match('src="https://example.com/assets/application.js', last_response.body)
     end
 
     test "asset URLs should be protocol-relative if no request is in scope" do