diff --git a/hgext/phabricator.py b/hgext/phabricator.py
--- a/hgext/phabricator.py
+++ b/hgext/phabricator.py
@@ -238,8 +238,8 @@
 
     def decorate(fn):
         def inner(*args, **kwargs):
-            cassette = pycompat.fsdecode(kwargs.pop('test_vcr', None))
-            if cassette:
+            if kwargs.get('test_vcr'):
+                cassette = pycompat.fsdecode(kwargs.pop('test_vcr'))
                 import hgdemandimport
 
                 with hgdemandimport.deactivated():