diff --git a/lib/ace/layer/font_metrics.js b/lib/ace/layer/font_metrics.js
index 7e71f8a8..715c6cf3 100644
--- a/lib/ace/layer/font_metrics.js
+++ b/lib/ace/layer/font_metrics.js
@@ -120,9 +120,9 @@ var FontMetrics = exports.FontMetrics = function(parentEl, interval) {
     this.setPolling = function(val) {
         if (val) {
             this.$pollSizeChanges();
-        } else {
-            if (this.$pollSizeChangesTimer)
-                this.$pollSizeChangesTimer;
+        } else if (this.$pollSizeChangesTimer) {
+            clearInterval(this.$pollSizeChangesTimer);
+            this.$pollSizeChangesTimer = 0;
         }
     };