1 files changed, 1 insertions, 1 deletions
diff --git a/bottle.py b/bottle.py
index 01b581e..f254bac 100644
--- a/bottle.py
+++ b/bottle.py
@@ -3156,7 +3156,7 @@ class FileCheckerThread(threading.Thread):
         files = dict()
 
         for module in list(sys.modules.values()):
-            path = getattr(module, '__file__', '')
+            path = getattr(module, '__file__', '') or ''
             if path[-4:] in ('.pyo', '.pyc'): path = path[:-1]
             if path and exists(path): files[path] = mtime(path)