1 files changed, 2 insertions, 0 deletions
diff --git a/railties/lib/generators/rails/app/app_generator.rb b/railties/lib/generators/rails/app/app_generator.rb
index 92e0d37436..888e3b2ddd 100644
--- a/railties/lib/generators/rails/app/app_generator.rb
+++ b/railties/lib/generators/rails/app/app_generator.rb
@@ -220,6 +220,8 @@ module Rails::Generators
           raise Error, "Invalid application name #{app_name}. Please give a name which does not start with numbers."
         elsif RESERVED_NAMES.include?(app_name)
           raise Error, "Invalid application name #{app_name}. Please give a name which does not match one of the reserved rails words."
+        elsif Object.const_defined?(app_const_base)
+          raise Error, "Invalid application name #{app_name}, constant #{app_const_base} is already in use. Please choose another application name."
         end
       end