diff --git a/feeds.module b/feeds.module
index 8785f22..834d27f 100644
--- a/feeds.module
+++ b/feeds.module
@@ -993,7 +993,7 @@ function feeds_valid_url($url, $absolute = FALSE) {
         (?:[\w\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})+@          # combination
       )?
       (?:
-        (?:[a-z0-9\-\.]|%[0-9a-f]{2})+                        # A domain name or a IPv4 address
+        (?:[a-z0-9\-\_\.]|%[0-9a-f]{2})+                      # A domain name or a IPv4 address
         |(?:\[(?:[0-9a-f]{0,4}:)*(?:[0-9a-f]{0,4})\])         # or a well formed IPv6 address
       )
       (?::[0-9]+)?                                            # Server port number (optional)