diff --git a/lib/urlapi.c b/lib/urlapi.c
index 479596acd1..2a36de6a58 100644
--- a/lib/urlapi.c
+++ b/lib/urlapi.c
@@ -678,8 +678,8 @@ static CURLUcode hostname_check(struct Curl_URL *u, char *hostname)
 #endif
   }
   else {
-    /* letters from the second string is not ok */
-    len = strcspn(hostname, " \r\n");
+    /* letters from the second string are not ok */
+    len = strcspn(hostname, " \r\n\t/:#?!@");
     if(hlen != len)
       /* hostname with bad content */
       return CURLUE_BAD_HOSTNAME;