--- a/accessible/generic/DocAccessible.cpp
+++ b/accessible/generic/DocAccessible.cpp
@@ -1979,25 +1979,27 @@ DocAccessible::ContentRemoved(Accessible
 
 #ifdef A11Y_LOG
   logging::TreeInfo("process content removal", 0,
                     "container", parent, "child", aChild, nullptr);
 #endif
 
   TreeMutation mt(parent);
   mt.BeforeRemoval(aChild);
+  MOZ_DIAGNOSTIC_ASSERT(aChild->Parent(), "Unparented #1");
 
   if (aChild->IsRelocated()) {
     nsTArray<RefPtr<Accessible> >* owned = mARIAOwnsHash.Get(parent);
     MOZ_ASSERT(owned, "IsRelocated flag is out of sync with mARIAOwnsHash");
     owned->RemoveElement(aChild);
     if (owned->Length() == 0) {
       mARIAOwnsHash.Remove(parent);
     }
   }
+  MOZ_DIAGNOSTIC_ASSERT(aChild->Parent(), "Unparented #2");
   parent->RemoveChild(aChild);
   UncacheChildrenInSubtree(aChild);
 
   mt.Done();
 }
 
 void
 DocAccessible::ContentRemoved(nsIContent* aContentNode)