diff --git a/usr/local/pkg/carp_settings.xml b/usr/local/pkg/carp_settings.xml
index cb34bb5b50..95c00dce6a 100644
--- a/usr/local/pkg/carp_settings.xml
+++ b/usr/local/pkg/carp_settings.xml
@@ -160,6 +160,12 @@
 		if($_POST["synchronizetoip"])
 			if(!is_ipaddr($_POST["synchronizetoip"]))
 				$input_errors[] = "You must specify a valid IP address.";
+		$ifdescrs = array('lan','wan');
+		for ($j = 1; isset($config['interfaces']['opt' . $j]); $j++) 
+			$ifdescrs['opt' . $j] = "opt" . $j;
+		foreach($ifdescrs as $descr) 
+			if($config['interfaces']['$descr']['ipaddr'] == $_POST["synchronizetoip"]) 
+				$input_errors[] = "CARP sync IP must be the backup firewall ip!  You cannot specify this firewalls IP in this location.";			
 	</custom_php_validation_command>
 	<custom_add_php_command_late>
 		/* setup carp interfaces */