1 files changed, 9 insertions, 16 deletions
diff --git a/src/directives.js b/src/directives.js
index 6fc19eaf..d800aa80 100644
--- a/src/directives.js
+++ b/src/directives.js
@@ -565,25 +565,18 @@ angularDirective("ng:submit", function(expression, element) {
   });
 });
 
+
 function ngClass(selector) {
   return function(expression, element){
+    var existing = element[0].className + ' ';
     return function(element){
-      if(selector(this.$index)) {
-        this.$watch(expression, function(newCls, oldCls) {
-          var cls = element.attr('class');
-          if (isArray(newCls)) newCls = newCls.join(' ');
-          if (isArray(oldCls)) oldCls = oldCls.join(' ');
-
-          // The time when newCls == oldCLs is when $watch just started
-          if (newCls == oldCls) {
-            cls += ' ' + newCls;
-          } else {
-            cls = cls.replace(' ' + oldCls, ' ' + newCls);
-          }
-
-          element.attr('class', cls);
-        });
-      }
+      this.$onEval(function(){
+        if (selector(this.$index)) {
+          var value = this.$eval(expression);
+          if (isArray(value)) value = value.join(' ');
+          element[0].className = trim(existing + value);
+        }
+      }, element);
     };
   };
 }