diff --git a/lib/datasource/docker.js b/lib/datasource/docker.js
index a7302d3863941cdf3d1ff683864f97d4c31324a1..5bb9b6fdd865e83cc139790a2e751cb1ac1d75f9 100644
--- a/lib/datasource/docker.js
+++ b/lib/datasource/docker.js
@@ -38,6 +38,7 @@ async function getAuthHeaders(registry, repository) {
       `Obtaining docker registry token for ${repository} using url ${authUrl}`
     );
     const { token } = (await got(authUrl, { json: true })).body;
+    // istanbul ignore if
     if (!token) {
       logger.warn('Failed to obtain docker registry token');
       return null;