1 files changed, 5 insertions, 1 deletions
diff --git a/accessible/base/EventQueue.h b/accessible/base/EventQueue.h
index 434acd3c09..87bcf89340 100644
--- a/accessible/base/EventQueue.h
+++ b/accessible/base/EventQueue.h
@@ -7,6 +7,7 @@
 #define mozilla_a11y_EventQueue_h_
 
 #include "AccEvent.h"
+#include "mozilla/Assertions.h"
 
 namespace mozilla {
 namespace a11y {
@@ -18,7 +19,10 @@ class DocAccessible;
  */
 class EventQueue {
  protected:
-  explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {}
+  explicit EventQueue(DocAccessible* aDocument) : mDocument(aDocument) {
+    MOZ_ASSERT(mDocument,
+               "There's no point creating an event queue for a null document");
+  }
 
   /**
    * Put an accessible event into the queue to process it later.