diff --git a/apps/wpm/serializers.py b/apps/wpm/serializers.py
index 9908d6c2..0254db34 100644
--- a/apps/wpm/serializers.py
+++ b/apps/wpm/serializers.py
@@ -880,9 +880,12 @@ class MlogbwCreateUpdateSerializer(CustomModelSerializer):
     def update(self, instance, validated_data):
         validated_data.pop("mlogb")
         ftest_data = validated_data.pop("ftest", None)
-        mlogbw = super().update(instance, validated_data)
+        mlogbw:Mlogbw = super().update(instance, validated_data)
         if ftest_data:
             mlogbw = self.save_ftest(mlogbw, ftest_data)
+        elif ftest_data is None:
+            if mlogbw.ftest:
+                mlogbw.ftest.delete()
         return mlogbw
 
 class MlogbOutUpdateSerializer(CustomModelSerializer):