diff --git a/web/pdf_history.js b/web/pdf_history.js
index 0edc0933f..7b5e11513 100644
--- a/web/pdf_history.js
+++ b/web/pdf_history.js
@@ -109,7 +109,7 @@ class PDFHistory {
     this._currentHash = getCurrentHash();
     this._numPositionUpdates = 0;
 
-    this._uid = 0;
+    this._uid = this._maxUid = 0;
     this._destination = null;
     this._position = null;
 
@@ -245,7 +245,7 @@ class PDFHistory {
       return;
     }
     let state = window.history.state;
-    if (this._isValidState(state) && state.uid < (this._uid - 1)) {
+    if (this._isValidState(state) && state.uid < this._maxUid) {
       window.history.forward();
     }
   }
@@ -286,6 +286,8 @@ class PDFHistory {
         window.history.replaceState(newState, '', document.URL);
       }
     } else {
+      this._maxUid = this._uid;
+
       if (typeof PDFJSDev !== 'undefined' &&
           PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
         // Providing the third argument causes a SecurityError for file:// URLs.