diff --git a/web/interfaces.js b/web/interfaces.js
index d90245825..170622681 100644
--- a/web/interfaces.js
+++ b/web/interfaces.js
@@ -20,6 +20,11 @@
  * @interface
  */
 class IPDFLinkService {
+  /**
+   * @returns {number}
+   */
+  get pagesCount() {}
+
   /**
    * @returns {number}
    */
diff --git a/web/pdf_link_service.js b/web/pdf_link_service.js
index 985be38cd..4862dfc0e 100644
--- a/web/pdf_link_service.js
+++ b/web/pdf_link_service.js
@@ -408,12 +408,22 @@ function isValidExplicitDestination(dest) {
   return true;
 }
 
+/**
+ * @implements {IPDFLinkService}
+ */
 class SimpleLinkService {
   constructor() {
     this.externalLinkTarget = null;
     this.externalLinkRel = null;
   }
 
+  /**
+   * @returns {number}
+   */
+  get pagesCount() {
+    return 0;
+  }
+
   /**
    * @returns {number}
    */