diff --git a/server/lib/user-agent.js b/server/lib/user-agent.js
index fe8aeee46a..4f10da24c9 100644
--- a/server/lib/user-agent.js
+++ b/server/lib/user-agent.js
@@ -34,7 +34,7 @@ function safeFamily (parent) {
 }
 
 function safeVersion (parent) {
-  if (! VALID_VERSION.test(parent.toVersionString())) {
+  if (parent && parent.toVersionString && ! VALID_VERSION.test(parent.toVersionString())) {
     parent.major = parent.minor = parent.patch = parent.patchMinor = null;
   }
 }