diff --git a/lib/lrama/output.rb b/lib/lrama/output.rb
index 757d16e2..2dcdae7b 100644
--- a/lib/lrama/output.rb
+++ b/lib/lrama/output.rb
@@ -252,7 +252,7 @@ def user_args
     end
 
     def extract_param_name(param)
-      /\A(\W*)([a-zA-Z0-9_]+)\z/.match(param.split.last)[2]
+      param[/\b([a-zA-Z0-9_]+)(?=\s*\z)/]
     end
 
     def parse_param_name