diff --git a/tests/unit/style/viewport.rs b/tests/unit/style/viewport.rs
index 1e7cfe4cd93..35a0ac432c3 100644
--- a/tests/unit/style/viewport.rs
+++ b/tests/unit/style/viewport.rs
@@ -172,6 +172,7 @@ fn cascading_within_viewport_rule() {
 
 #[test]
 fn multiple_stylesheets_cascading() {
+    ::util::opts::set_experimental_enabled(true);
     let device = Device::new(MediaType::Screen, Size2D::typed(800., 600.));
 
     let stylesheets = vec![