1 files changed, 3 insertions, 2 deletions
diff --git a/Source/JavaScriptCore/heap/MarkStack.cpp b/Source/JavaScriptCore/heap/MarkStack.cpp
index 9d3062154..9a4a01f04 100644
--- a/Source/JavaScriptCore/heap/MarkStack.cpp
+++ b/Source/JavaScriptCore/heap/MarkStack.cpp
@@ -35,10 +35,9 @@
 #include "JSArray.h"
 #include "JSCell.h"
 #include "JSObject.h"
-#include "ScopeChain.h"
+
 #include "SlotVisitorInlineMethods.h"
 #include "Structure.h"
-#include "UString.h"
 #include "WriteBarrier.h"
 #include <wtf/Atomics.h>
 #include <wtf/DataLog.h>
@@ -523,6 +522,8 @@ ALWAYS_INLINE void MarkStack::internalAppend(JSValue* slot)
         return;
 
     JSCell* cell = value.asCell();
+    if (!cell)
+        return;
 
     if (m_shouldHashConst && cell->isString()) {
         JSString* string = jsCast<JSString*>(cell);