diff --git a/aio/src/app/layout/doc-viewer/doc-viewer.component.ts b/aio/src/app/layout/doc-viewer/doc-viewer.component.ts
index 3915a2ad9f..e13cefffd6 100644
--- a/aio/src/app/layout/doc-viewer/doc-viewer.component.ts
+++ b/aio/src/app/layout/doc-viewer/doc-viewer.component.ts
@@ -206,7 +206,7 @@ export class DocViewerComponent implements OnDestroy {
                     // setting each style.
                     switchMap(() => raf$), tap(() => elem.style[prop] = from),
                     switchMap(() => raf$), tap(() => elem.style.transition = `all ${duration}ms ease-in-out`),
-                    switchMap(() => raf$), tap(() => (elem.style as any)[prop] = to),
+                    switchMap(() => raf$), tap(() => elem.style[prop] = to),
                     switchMap(() => timer(getActualDuration(elem))), switchMap(() => this.void$),
                 );
         };