diff --git a/daklib/checks.py b/daklib/checks.py
index 6091bc73f60deca61c50a74155022fd0bd475f45..63b56da6c0b3c4f771f8070d58e53db4e10d81b4 100644
--- a/daklib/checks.py
+++ b/daklib/checks.py
@@ -471,6 +471,7 @@ class TransitionCheck(Check):
         if transitions is None:
             return True
 
+        control = upload.changes.changes
         source = re_field_source.match(control['Source']).group('package')
 
         for trans in transitions: