diff --git a/lib/datasource/npm/get.js b/lib/datasource/npm/get.js
index 98640d22720888da422d9f5f94c6ac71327611e0..90a4b8817138d4eaf30748d6dc22d635f0c2ad4a 100644
--- a/lib/datasource/npm/get.js
+++ b/lib/datasource/npm/get.js
@@ -67,6 +67,10 @@ async function getDependency(name, maxRetries = 5) {
       authInfo.type = 'Basic';
     }
     headers.authorization = `${authInfo.type} ${authInfo.token}`;
+    logger.debug(
+      { token: maskToken(authInfo.token), npmName: name },
+      'Using auth for npm lookup'
+    );
   } else if (process.env.NPM_TOKEN && process.env.NPM_TOKEN !== 'undefined') {
     headers.authorization = `Bearer ${process.env.NPM_TOKEN}`;
   }