diff --git a/packages/pdfjs-viewer/src/custom.ts b/packages/pdfjs-viewer/src/custom.ts
index 99efe60fa2..ad781a7872 100644
--- a/packages/pdfjs-viewer/src/custom.ts
+++ b/packages/pdfjs-viewer/src/custom.ts
@@ -42,7 +42,7 @@ async function main() {
 };
 
 function configurePdfViewerOptions() {
-    const pdfOptionsHandler = (event) => {
+    const pdfOptionsHandler = (event: CustomEvent) => {
         if (event.detail?.source === window && window.PDFViewerApplicationOptions) {
             window.PDFViewerApplicationOptions.set("disablePreferences", true);
             window.PDFViewerApplicationOptions.set("enableHighlightFloatingButton", true);
diff --git a/packages/pdfjs-viewer/src/typings.d.ts b/packages/pdfjs-viewer/src/typings.d.ts
index 50ac44fc07..db12b178d0 100644
--- a/packages/pdfjs-viewer/src/typings.d.ts
+++ b/packages/pdfjs-viewer/src/typings.d.ts
@@ -46,5 +46,6 @@ declare global {
             };
             store: ViewHistory;
         };
+        PDFViewerApplicationOptions?: { set(name: string, value: any): void; }
     }
 }