diff --git a/test/ModelSpec.hs b/test/ModelSpec.hs
index 1e2940125..9f156a1f6 100644
--- a/test/ModelSpec.hs
+++ b/test/ModelSpec.hs
@@ -64,6 +64,7 @@ instance Arbitrary Sheet where
     <*> arbitrary
     <*> arbitrary
     <*> arbitrary
+    <*> arbitrary
   shrink = genericShrink
 
 instance Arbitrary Tutorial where