diff --git a/tests/position-floating-panel.test.mjs b/tests/position-floating-panel.test.mjs
index bdc76666..a459e59c 100644
--- a/tests/position-floating-panel.test.mjs
+++ b/tests/position-floating-panel.test.mjs
@@ -75,6 +75,7 @@ beforeEach(async () => {
   global.HTMLElement = windowRef.HTMLElement;
   global.Element = windowRef.Element;
   global.Node = windowRef.Node;
+  global.HTMLStyleElement = windowRef.HTMLStyleElement;
   global.getComputedStyle = windowRef.getComputedStyle.bind(windowRef);
   global.ResizeObserver = StubObserver;
   if (!global.PointerEvent) {