diff --git a/browser/components/wintaskbar/test/browser_taskbar_preview.js b/browser/components/wintaskbar/test/browser_taskbar_preview.js
index 507046db8b3..dfb08fe45c3 100644
--- a/browser/components/wintaskbar/test/browser_taskbar_preview.js
+++ b/browser/components/wintaskbar/test/browser_taskbar_preview.js
@@ -1,6 +1,4 @@
 function test() {
-  waitForExplicitFinish();
-
   // Cannot do anything if the taskbar service is not available
   ok(("AeroPeek" in window) == isWin7OrHigher(), "AeroPeek initialized when it should be");
 
@@ -8,6 +6,8 @@ function test() {
   if (!("AeroPeek" in window))
     return;
 
+  waitForExplicitFinish();
+
   gPrefService.setBoolPref("aeropeek.enable", true);
 
   is(1, AeroPeek.windows.length, "Got the expected number of windows");