diff --git a/lib/client/udp-tracker.js b/lib/client/udp-tracker.js
index 2402dbf..d16427d 100644
--- a/lib/client/udp-tracker.js
+++ b/lib/client/udp-tracker.js
@@ -130,7 +130,11 @@ class UDPTracker extends Tracker {
       cleanup()
       if (self.destroyed) return
 
-      if (err.message) err.message += ` (${self.announceUrl})`
+      try {
+        // Error.message is readonly on some platforms.
+        if (err.message) err.message += ` (${self.announceUrl})`
+      } catch (ignored) {
+      }
       // errors will often happen if a tracker is offline, so don't treat it as fatal
       self.client.emit('warning', err)
     }