diff --git a/test/integration/spanner_test.js b/test/integration/spanner_test.js
index 71a5ac0..93b5d4d 100644
--- a/test/integration/spanner_test.js
+++ b/test/integration/spanner_test.js
@@ -22,7 +22,7 @@
 
 'use strict';
 
-const PROTO_DIR = __dirname + '../../third_party/googleapis';
+const PROTO_DIR = __dirname + '/../../third_party/googleapis';
 
 const protoLoader = require('@grpc/proto-loader');
 const assert = require('assert');