--- a/xpcom/tests/unit/test_nsIProcess.js
+++ b/xpcom/tests/unit/test_nsIProcess.js
@@ -230,29 +230,37 @@ function test_notify_killed()
 
   process.kill();
 }
 
 // test if killing a process that is already finished doesn't crash
 function test_kill_2()
 {
   var file = get_test_program("TestQuickReturn");
+  var thread = Components.classes["@mozilla.org/thread-manager;1"]
+                         .getService().currentThread;
 
   for (var i = 0; i < 1000; i++) {
     var process = Components.classes["@mozilla.org/process/util;1"]
                           .createInstance(Components.interfaces.nsIProcess);
     process.init(file);
 
     process.run(false, [], 0);
 
     try {
       process.kill();
     }
     catch (e) { }
   }
+
+  // We need to ensure that we process any events on the main thread -
+  // this allow threads to clean up properly and avoid out of memory
+  // errors during the test.
+  while (thread.hasPendingEvents())
+    thread.processNextEvent(false);
 }
 
 function run_test() {
   set_environment();
   test_kill();
   test_quick();
   test_arguments();
   test_unicode_arguments();