--- mytop-1.7/mytop.orig	2009-03-21 16:31:23.000000000 +0100
+++ mytop-1.7/mytop	2010-05-09 15:10:33.000000000 +0200
@@ -955,8 +955,11 @@
         {
             $thread->{Host} =~ s/:\d+$//;
             my $host = gethostbyaddr(inet_aton($thread->{Host}), AF_INET);
-            $host =~ s/^([^.]+).*/$1/;
-            $thread->{Host} = $host;
+            if (defined $host)
+            {
+                $host =~ s/^([^.]+).*/$1/;
+                $thread->{Host} = $host;
+            }
         }
 
         ## Fix possible undefs