--- a/browser/components/sessionstore/content/content-sessionStore.js
+++ b/browser/components/sessionstore/content/content-sessionStore.js
@@ -685,17 +685,17 @@ var MessageQueue = {
 
   /**
    * Disables sending batched messages on a timer. Also cancels any pending
    * timers.
    */
   set timeoutDisabled(val) {
     this._timeoutDisabled = val;
 
-    if (!val && this._timeout) {
+    if (val && this._timeout) {
       clearTimeout(this._timeout);
       this._timeout = null;
     }
 
     return val;
   },
 
   init() {