diff --git a/tcllib/devlist.py b/tcllib/devlist.py
index 89cde77..64dbf68 100644
--- a/tcllib/devlist.py
+++ b/tcllib/devlist.py
@@ -35,7 +35,7 @@ class DevListMixin:
             prds = json.load(df)
 
         if old_prds and output_diff:
-            DevList.print_prd_diff(old_prds, prds)
+            DevListMixin.print_prd_diff(old_prds, prds)
 
         return prds