diff --git a/web/app.js b/web/app.js
index 3b0aecd3e..fd42d2bfa 100644
--- a/web/app.js
+++ b/web/app.js
@@ -412,6 +412,9 @@ let PDFViewerApplication = {
   },
 
   zoomIn(ticks) {
+    if (this.pdfViewer.isInPresentationMode) {
+      return;
+    }
     let newScale = this.pdfViewer.currentScale;
     do {
       newScale = (newScale * DEFAULT_SCALE_DELTA).toFixed(2);
@@ -422,6 +425,9 @@ let PDFViewerApplication = {
   },
 
   zoomOut(ticks) {
+    if (this.pdfViewer.isInPresentationMode) {
+      return;
+    }
     let newScale = this.pdfViewer.currentScale;
     do {
       newScale = (newScale / DEFAULT_SCALE_DELTA).toFixed(2);