diff --git a/ddclient.in b/ddclient.in
index 36bda0d..d446146 100755
--- a/ddclient.in
+++ b/ddclient.in
@@ -2212,6 +2212,10 @@ sub get_ip {
 
     if ($use eq 'ip') {
         $ip  = opt('ip', $h);
+        if (!is_ipv4($ip) && !is_ipv6($ip)) {
+            warning("'%s' is not a valid IPv4 or IPv6 address", $ip);
+            $ip = undef;
+        }
         $arg = 'ip';
 
     } elsif ($use eq 'if') {