diff --git a/articles/models.py b/articles/models.py
index 94ea88d..4d201da 100644
--- a/articles/models.py
+++ b/articles/models.py
@@ -513,7 +513,7 @@ def filename(self):
 
     @property
     def content_type_class(self):
-        mt = mimetypes.guess_type(self.attachment.path)[0]
+        mt = mimetypes.guess_type(self.uploadedfile.url)[0]
         if mt:
             content_type = mt.replace('/', '_')
         else: