diff --git a/lib/javascript-static.js b/lib/javascript-static.js
index 463f8249616..f8027763d53 100644
--- a/lib/javascript-static.js
+++ b/lib/javascript-static.js
@@ -1182,13 +1182,23 @@ function openpopup(event, args) {
     if (!args.url.match(/https?:\/\//)) {
         fullurl = M.cfg.wwwroot + args.url;
     }
+    if (args.fullscreen) {
+        args.options = args.options.
+                replace(/top=\d+/, 'top=0').
+                replace(/left=\d+/, 'left=0').
+                replace(/width=\d+/, 'width=' + screen.availWidth).
+                replace(/height=\d+/, 'height=' + screen.availHeight);
+    }
     var windowobj = window.open(fullurl,args.name,args.options);
     if (!windowobj) {
         return true;
     }
+
     if (args.fullscreen) {
-        windowobj.moveTo(0,0);
-        windowobj.resizeTo(screen.availWidth,screen.availHeight);
+        setTimeout(function() {
+            windowobj.moveTo(0, 0);
+            windowobj.resizeTo(screen.availWidth, screen.availHeight)
+        }, 0);
     }
     windowobj.focus();