diff --git a/spec/module-cache-spec.coffee b/spec/module-cache-spec.coffee
index e75a1cf56..5cf6bd2fd 100644
--- a/spec/module-cache-spec.coffee
+++ b/spec/module-cache-spec.coffee
@@ -14,6 +14,7 @@ describe 'ModuleCache', ->
 
     for builtinName, builtinPath of builtins
       expect(require.resolve(builtinName)).toBe builtinPath
+      expect(fs.isFileSync(require.resolve(builtinName)))
 
     expect(Module._findPath.callCount).toBe 0