diff --git a/searx/webapp.py b/searx/webapp.py
index 4e0e2cb82..3da0df8b4 100755
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -1321,15 +1321,15 @@ function modal_open(url, num)
         var iframe = document.querySelector("#iframe-wrapper > iframe");
         if(num=='pdf')
         {
+            var pdf = iframe.contentWindow.PDFViewerApplication.pdfDocument;
             new Promise((resolve, reject) => {
                     const interval = setInterval(() => {
-                    if (numPages !== null) {
+                    if (pdf.numPages) {
                         clearInterval(interval);
-                        resolve(numPages);
+                        resolve(pdf.numPages);
                     }
                     }, 1000); // 定期检查 numPages 是否不为 null，这里是每隔1秒检查一次
                 }).then( function foo(){
-            var pdf = iframe.contentWindow.PDFViewerApplication.pdfDocument;
             var numPages = pdf.numPages; //获取总页数
             var promises = []; //用来存放每一页的Promise对象
             sentences=[]
diff --git a/searx/webapp1.py b/searx/webapp1.py
index 4e0e2cb82..3da0df8b4 100644
--- a/searx/webapp1.py
+++ b/searx/webapp1.py
@@ -1321,15 +1321,15 @@ function modal_open(url, num)
         var iframe = document.querySelector("#iframe-wrapper > iframe");
         if(num=='pdf')
         {
+            var pdf = iframe.contentWindow.PDFViewerApplication.pdfDocument;
             new Promise((resolve, reject) => {
                     const interval = setInterval(() => {
-                    if (numPages !== null) {
+                    if (pdf.numPages) {
                         clearInterval(interval);
-                        resolve(numPages);
+                        resolve(pdf.numPages);
                     }
                     }, 1000); // 定期检查 numPages 是否不为 null，这里是每隔1秒检查一次
                 }).then( function foo(){
-            var pdf = iframe.contentWindow.PDFViewerApplication.pdfDocument;
             var numPages = pdf.numPages; //获取总页数
             var promises = []; //用来存放每一页的Promise对象
             sentences=[]