diff --git a/apps/wpm/filters.py b/apps/wpm/filters.py
index 8dc9dd13..22c49b2d 100644
--- a/apps/wpm/filters.py
+++ b/apps/wpm/filters.py
@@ -93,7 +93,7 @@ class WMaterialFilter(filters.FilterSet):
             "notok_sign": ["exact", "in", "isnull"],
             "count_xtest": ["gte", "isnull"],
             "supplier": ["exact"],
-            "defect": ["exact"]
+            "defect": ["exact", "isnull"]
         }
 
 class MlogFilter(filters.FilterSet):