diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index 8e9083e6eb4c60129f60a196138486246940ca0e..bb2a9fcf221138bb42887c92c9098b23d2c7e54a 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -225,7 +225,7 @@ def javascript_runtime_gemfile_entry
         if defined?(JRUBY_VERSION)
           "gem 'therubyrhino'\n"
         else
-          "# gem 'therubyracer'\n"
+          "# gem 'therubyracer', :platform => :ruby\n"
         end
       end