diff --git a/dicom-viewer/src/App.tsx b/dicom-viewer/src/App.tsx
index 449fac7..cf00507 100644
--- a/dicom-viewer/src/App.tsx
+++ b/dicom-viewer/src/App.tsx
@@ -4232,7 +4232,7 @@ function App({ container_id, imageStacks, autoCacheStack, annotationJson, viewer
           onMouseEnter={() => setGridBtnActive(true)}
           onMouseLeave={() => setGridBtnActive(false)}
           onClick={() => {
-            const root = document.querySelector(".dicom-viewer-root") as HTMLElement;
+            const root = appRootRef.current;
             if (!root) return;
             if (document.fullscreenElement === root) {
               document.exitFullscreen();