diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 2b81c08..ab5efb0 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -90,7 +90,11 @@
 // MacroAssembler implements a collection of frequently used macros.
 class MacroAssembler: public Assembler {
  public:
-  MacroAssembler(void* buffer, int size);
+  // The isolate parameter can be NULL if the macro assembler should
+  // not use isolate-dependent functionality. In this case, it's the
+  // responsibility of the caller to never invoke such function on the
+  // macro assembler.
+  MacroAssembler(Isolate* isolate, void* buffer, int size);
 
   // Jump, Call, and Ret pseudo instructions implementing inter-working.
   void Jump(Register target, Condition cond = al);
@@ -781,7 +785,10 @@
   // Store the function for the given builtin in the target register.
   void GetBuiltinFunction(Register target, Builtins::JavaScript id);
 
-  Handle<Object> CodeObject() { return code_object_; }
+  Handle<Object> CodeObject() {
+    ASSERT(!code_object_.is_null());
+    return code_object_;
+  }
 
 
   // ---------------------------------------------------------------------------