diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -325,7 +325,7 @@ class mapfile(dict):
         self._read()
 
     def _read(self):
-        if self.path is None:
+        if not self.path:
             return
         try:
             fp = open(self.path, 'r')