diff --git a/lib/galaxy/tools/toolbox/watcher.py b/lib/galaxy/tools/toolbox/watcher.py
index ef4b65947bd..554f2d7a94e 100644
--- a/lib/galaxy/tools/toolbox/watcher.py
+++ b/lib/galaxy/tools/toolbox/watcher.py
@@ -9,6 +9,7 @@ try:
     from watchdog.observers.polling import PollingObserver
     can_watch = True
 except ImportError:
+    Observer = None
     FileSystemEventHandler = object
     PollingObserver = object
     can_watch = False