diff --git a/JavaScriptCore/kjs/function.cpp b/JavaScriptCore/kjs/function.cpp
index a9fef6e..b31ac88 100644
--- a/JavaScriptCore/kjs/function.cpp
+++ b/JavaScriptCore/kjs/function.cpp
@@ -86,7 +86,10 @@ JSValue* FunctionImp::callAsFunction(ExecState* exec, JSObject* thisObj, const L
     RegisterFileStack* stack = &exec->dynamicGlobalObject()->registerFileStack();
     RegisterFile* current = stack->current();
     if (!current->safeForReentry()) {
-        stack->pushFunctionRegisterFile();
+        RegisterFile* file = stack->pushFunctionRegisterFile();
+        ASSERT(file == stack->current());
+        ASSERT(file->safeForReentry());
+        ASSERT(stack->current()->safeForReentry());
         JSValue* result = machine().execute(body.get(), exec, this, thisObj, args, stack, _scope.node(), &exception);
         stack->popFunctionRegisterFile();
         exec->setException(exception);