diff --git a/lib/Slic3r/Test.pm b/lib/Slic3r/Test.pm
index 319214997..f4942d0c3 100644
--- a/lib/Slic3r/Test.pm
+++ b/lib/Slic3r/Test.pm
@@ -34,7 +34,7 @@ sub model {
     $object->add_volume(facets => $facets);
     $object->add_instance(
         offset      => [0,0],
-        rotation    => $params{rotation},
+        rotation    => $params{rotation} // 0,
     );
     return $model;
 }