diff --git a/test/Model/TypesSpec.hs b/test/Model/TypesSpec.hs
index 8a38486ff..9f5598b68 100644
--- a/test/Model/TypesSpec.hs
+++ b/test/Model/TypesSpec.hs
@@ -406,6 +406,7 @@ instance Arbitrary SheetAuthorshipStatementMode where
 instance Arbitrary LmsStatus where
   arbitrary = genericArbitrary
 
+deriving newtype instance Arbitrary LmsIdent
 
 spec :: Spec
 spec = do