diff --git a/web/pdf_viewer.js b/web/pdf_viewer.js
index 0e4f97391..9aa3a4189 100644
--- a/web/pdf_viewer.js
+++ b/web/pdf_viewer.js
@@ -662,7 +662,7 @@ var PDFViewer = (function pdfViewer() {
     },
 
     get isChangingPresentationMode() {
-      return this.PresentationModeState === PresentationModeState.CHANGING;
+      return this.presentationModeState === PresentationModeState.CHANGING;
     },
 
     get isHorizontalScrollbarEnabled() {