diff --git a/toolkit/mozapps/update/content/updates.js b/toolkit/mozapps/update/content/updates.js
index 5402591224b5..5997d4730906 100644
--- a/toolkit/mozapps/update/content/updates.js
+++ b/toolkit/mozapps/update/content/updates.js
@@ -1194,7 +1194,7 @@ var gDownloadingPage = {
    * Member variables for updating download status
    */
   _lastSec: Infinity,
-  _startTime: Date.now(),
+  _startTime: null,
   _pausedStatus: "",
 
   /**
@@ -1227,6 +1227,8 @@ var gDownloadingPage = {
       return;
     }
 
+    this._startTime = Date.now();
+
     try {
       // Say that this was a foreground download, not a background download,
       // since the user cared enough to look in on this process.