diff --git a/test/ModelSpec.hs b/test/ModelSpec.hs
index 67196ba0a..1e2940125 100644
--- a/test/ModelSpec.hs
+++ b/test/ModelSpec.hs
@@ -63,6 +63,7 @@ instance Arbitrary Sheet where
     <*> arbitrary
     <*> arbitrary
     <*> arbitrary
+    <*> arbitrary
   shrink = genericShrink
 
 instance Arbitrary Tutorial where