diff --git a/test/ModelSpec.hs b/test/ModelSpec.hs
index 9f156a1f6..148c8c064 100644
--- a/test/ModelSpec.hs
+++ b/test/ModelSpec.hs
@@ -64,7 +64,7 @@ instance Arbitrary Sheet where
     <*> arbitrary
     <*> arbitrary
     <*> arbitrary
-    <*> arbitrary
+    <*> return Nothing
   shrink = genericShrink
 
 instance Arbitrary Tutorial where