diff --git a/web/viewer.js b/web/viewer.js
index b3713770b..f8b689cb4 100644
--- a/web/viewer.js
+++ b/web/viewer.js
@@ -1047,6 +1047,11 @@ var PDFView = {
     // updated if the zoom level stayed the same.
     this.currentScale = 0;
     this.currentScaleValue = null;
+    // When opening a new file (when one is already loaded in the viewer):
+    // Reset 'currentPageNumber', since otherwise the page's scale will be wrong
+    // if 'currentPageNumber' is larger than the number of pages in the file.
+    document.getElementById('pageNumber').value = currentPageNumber = 1;
+
     if (PDFHistory.initialDestination) {
       this.navigateTo(PDFHistory.initialDestination);
       PDFHistory.initialDestination = null;