diff --git a/src/objects.h b/src/objects.h
index 76d8351db1..147dc00d4c 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -3413,8 +3413,8 @@ class ScopeInfo : public FixedArray {
   // otherwise returns a value < 0. The name must be a symbol (canonicalized).
   int ParameterIndex(String* name);
 
-  // Lookup support for serialized scope info. Returns the
-  // function context slot index if the function name is present (named
+  // Lookup support for serialized scope info. Returns the function context
+  // slot index if the function name is present and context-allocated (named
   // function expressions, only), otherwise returns a value < 0. The name
   // must be a symbol (canonicalized).
   int FunctionContextSlotIndex(String* name, VariableMode* mode);
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 683fec15bb..e895cccdfc 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -2109,12 +2109,11 @@ void V8HeapExplorer::ExtractClosureReferences(JSObject* js_obj,
     // Add function variable.
     if (scope_info->HasFunctionName()) {
       String* name = scope_info->FunctionName();
-      int idx = Context::MIN_CONTEXT_SLOTS + context_locals;
-#ifdef DEBUG
       VariableMode mode;
-      ASSERT(idx == scope_info->FunctionContextSlotIndex(name, &mode));
-#endif
-      SetClosureReference(js_obj, entry, name, context->get(idx));
+      int idx = scope_info->FunctionContextSlotIndex(name, &mode);
+      if (idx >= 0) {
+        SetClosureReference(js_obj, entry, name, context->get(idx));
+      }
     }
   }
 }