diff --git a/lib/device_detector.rb b/lib/device_detector.rb
index 9e9d37b..0659946 100644
--- a/lib/device_detector.rb
+++ b/lib/device_detector.rb
@@ -237,7 +237,7 @@ def linux_fix?
 
   # Related to issue mentionned in device.rb#1562
   def fix_for_x_music
-    user_agent.include?('X-music Ⅲ') ? 'X-Music III' : nil
+    user_agent&.include?('X-music Ⅲ') ? 'X-Music III' : nil
   end
 
   def skip_os_version?