--- a/testing/mochitest/browser-test.js
+++ b/testing/mochitest/browser-test.js
@@ -194,17 +194,19 @@ Tester.prototype = {
       this.currentTest.scope = null;
     }
 
     // Check the window state for the current test before moving to the next one.
     // This also causes us to check before starting any tests, since nextTest()
     // is invoked to start the tests.
     this.waitForWindowsState((function () {
       if (this.done) {
-        this.finish();
+        // Schedule GC before finishing in order to be able to report an accurate
+        // DOM window count at the end of this test suite.
+        Cu.schedulePreciseGC(this.finish.bind(this));
         return;
       }
 
       this.currentTestIndex++;
       this.execTest();
     }).bind(this));
   },