diff --git a/lib/ace/mode/xml_util.js b/lib/ace/mode/xml_util.js
index 2bd1bc8e..9632fddf 100644
--- a/lib/ace/mode/xml_util.js
+++ b/lib/ace/mode/xml_util.js
@@ -110,7 +110,7 @@ exports.tag = function(states, name, nextState) {
 			}
 		},		
         merge : true,
-        regex : "[-_a-zA-Z0-9:]+",
+        regex : "[-_a-zA-Z0-9:!]+",
         next : name + "embed-attribute-list" 
     }, {
         token: "empty",