diff --git a/runtime/syntax/ruby.yaml b/runtime/syntax/ruby.yaml
index 415ab925..dadb4c26 100644
--- a/runtime/syntax/ruby.yaml
+++ b/runtime/syntax/ruby.yaml
@@ -1,7 +1,7 @@
 filetype: ruby
 
 detect:
-    filename: '\.(rb|rake|gemspec)$|^(.*[\\/])?(Gemfile|config.ru|Rakefile|Capfile|Vagrantfile|Guardfile|Appfile|Fastfile|Pluginfile|Podfile|\.?[Bb]rewfile)$'
+    filename: '\.(rb|rake|gemspec)$|^(.*[\\/])?(Gemfile|config\.ru|Rakefile|Capfile|Vagrantfile|Guardfile|Appfile|Fastfile|Pluginfile|Podfile|\.?[Bb]rewfile)$'
     header: "^#!.*/(env +)?ruby( |$)"
 
 rules: