diff --git a/test/parallel/test-http-outgoing-proto.js b/test/parallel/test-http-outgoing-proto.js
index 53198708b42b68..dac93638673082 100644
--- a/test/parallel/test-http-outgoing-proto.js
+++ b/test/parallel/test-http-outgoing-proto.js
@@ -7,7 +7,8 @@ const OutgoingMessage = http.OutgoingMessage;
 const ClientRequest = http.ClientRequest;
 const ServerResponse = http.ServerResponse;
 
-assert.throws(OutgoingMessage.prototype._implicitHeader);
+assert.throws(OutgoingMessage.prototype._implicitHeader,
+              /^Error: _implicitHeader\(\) method is not implemented$/);
 assert.strictEqual(
   typeof ClientRequest.prototype._implicitHeader, 'function');
 assert.strictEqual(