diff --git a/cps/web.py b/cps/web.py
index 8d00ad53..27f5ce65 100755
--- a/cps/web.py
+++ b/cps/web.py
@@ -477,7 +477,7 @@ def yesno(value, yes, no):
 @app.template_filter('canread')
 @app.template_test('canread')
 def canread(ext):
-    if type(ext) == db.Data:
+    if isinstance(ext, db.Data):
         ext = ext.format
     return ext.lower() in READER_EXTENSIONS