diff --git a/ts_web/elements/viewer.ts b/ts_web/elements/viewer.ts
index 56ad083..c7a2fcc 100644
--- a/ts_web/elements/viewer.ts
+++ b/ts_web/elements/viewer.ts
@@ -1177,7 +1177,7 @@ export class DeDocumentViewer extends DeesElement {
         // Trigger re-render to update active thumbnail
         this.requestUpdate();
       };
-      viewport.addEventListener("scroll", scrollHandler);
+      viewport.addEventListener("scroll", scrollHandler, { passive: true });
       this.registerGarbageFunction(() => viewport.removeEventListener("scroll", scrollHandler));
     }