1 files changed, 5 insertions, 3 deletions
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 6a49f440f..b8cb1facb 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -640,9 +640,11 @@ IdleRequestExecutor::SetDeadline(TimeStamp aDeadline)
 void
 IdleRequestExecutor::MaybeDispatch()
 {
-  MOZ_DIAGNOSTIC_ASSERT(mWindow);
-
-  if (mDispatched) {
+  // If we've already dispatched the executor we don't want to do it
+  // again. Also, if we've called IdleRequestExecutor::Cancel mWindow
+  // will be null, which indicates that we shouldn't dispatch this
+  // executor either.
+  if (mDispatched || !mWindow) {
     return;
   }