diff --git a/lib/routes.js b/lib/routes.js
index c2f1958f..1c16440d 100644
--- a/lib/routes.js
+++ b/lib/routes.js
@@ -207,6 +207,6 @@ function session(req) {
 }
 
 function getFingerprint(req) {
-  return typeof req.connection.getPeerCertificate === 'function' &&
-    req.connection.getPeerCertificate().fingerprint;
+  return (typeof req.connection.getPeerCertificate === 'function' &&
+    req.connection.getPeerCertificate().fingerprint) || 'unknown';
 }