diff --git a/layout/base/FrameLayerBuilder.cpp b/layout/base/FrameLayerBuilder.cpp
index e87d9dc09..934d108e0 100644
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -272,8 +272,13 @@ FrameLayerBuilder::DisplayItemData::~DisplayItemData()
     array->RemoveElement(this);
   }
 
-  MOZ_RELEASE_ASSERT(sAliveDisplayItemDatas && sAliveDisplayItemDatas->Contains(this));
-  sAliveDisplayItemDatas->RemoveEntry(this);
+  MOZ_RELEASE_ASSERT(sAliveDisplayItemDatas);
+  nsPtrHashKey<mozilla::FrameLayerBuilder::DisplayItemData>* entry
+    = sAliveDisplayItemDatas->GetEntry(this);
+  MOZ_RELEASE_ASSERT(entry);
+
+  sAliveDisplayItemDatas->RemoveEntry(entry);
+
   if (sAliveDisplayItemDatas->Count() == 0) {
     delete sAliveDisplayItemDatas;
     sAliveDisplayItemDatas = nullptr;