diff --git a/test/ModelSpec.hs b/test/ModelSpec.hs
index 66b90b480..fb383203c 100644
--- a/test/ModelSpec.hs
+++ b/test/ModelSpec.hs
@@ -198,6 +198,10 @@ instance Arbitrary VerpMode where
   arbitrary = genericArbitrary
   shrink = genericShrink
 
+instance Arbitrary StudyModule where
+  arbitrary = genericArbitrary
+  shrink = genericShrink
+
 
 spec :: Spec
 spec = do