diff --git a/test/Utils/TypesSpec.hs b/test/Utils/TypesSpec.hs
index f5dfafb0f..80bd07ac2 100644
--- a/test/Utils/TypesSpec.hs
+++ b/test/Utils/TypesSpec.hs
@@ -14,6 +14,10 @@ instance Arbitrary SloppyBool where
   arbitrary = SloppyBool <$> arbitrary
   shrink (SloppyBool x) = SloppyBool <$> shrink x
 
+instance Arbitrary AvsInternalPersonalNo where 
+  arbitrary = canonical . AvsInternalPersonalNo <$> arbitrary
+  shrink (AvsInternalPersonalNo x) = canonical . AvsInternalPersonalNo <$> shrink x
+
 instance Arbitrary AvsPersonId where 
   arbitrary = AvsPersonId <$> arbitrary
   shrink (AvsPersonId x) = AvsPersonId <$> shrink x