diff --git a/program/js/app.js b/program/js/app.js
index 45e8dbeea..d6403f7ac 100644
--- a/program/js/app.js
+++ b/program/js/app.js
@@ -143,7 +143,7 @@ function rcube_webmail()
     this.task = this.env.task;
 
     // check browser
-    if (!bw.dom || !bw.xmlhttp_test() || (bw.mz && bw.vendver < 1.9) || (bw.ie && bw.vendver < 7)) {
+    if (this.env.server_error != 409 && (!bw.dom || !bw.xmlhttp_test() || (bw.mz && bw.vendver < 1.9) || (bw.ie && bw.vendver < 7))) {
       this.goto_url('error', '_code=0x199');
       return;
     }
@@ -6843,7 +6843,7 @@ function rcube_webmail()
         param[k] = query[k];
     }
 
-    return base + '&' + $.param(param) + querystring;
+    return base + (base.indexOf('?') > -1 ? '&' : '?') + $.param(param) + querystring;
   };
 
   this.redirect = function(url, lock)