diff --git a/lib/ace/mode/ruby_highlight_rules.js b/lib/ace/mode/ruby_highlight_rules.js
index 37549820..5b9038e5 100644
--- a/lib/ace/mode/ruby_highlight_rules.js
+++ b/lib/ace/mode/ruby_highlight_rules.js
@@ -110,7 +110,7 @@ RubyHighlightRules = function() {
 	                else if (buildinConstants[value])
 	                    return "constant.language";
                     else if (builtinVariables[value])
-                        return "invalid.illegal";
+                        return "variable.language";
                     else if (builtinFunctions[value])
                         return "support.function";
 	                else if (value == "debugger")