diff --git a/etc/inc/filter.inc b/etc/inc/filter.inc
index 0e081c2b1f..4bcd1cfe69 100644
--- a/etc/inc/filter.inc
+++ b/etc/inc/filter.inc
@@ -996,11 +996,12 @@ function filter_nat_rules_generate() {
 			if (isset($optcfg['enable']) && !$optcfg['bridge']) {
 				$optsa = gen_subnet($optcfg['ipaddr'], $optcfg['subnet']);
 				
-				/* setup nat mappings for lan -> optional interface */
-				if($optcfg['gateway'] <> "") {
+				/*    setup nat mappings for lan -> opt[$i]
+				 *    interface if a gateway is defined
+                                 */
+				if($optcfg['gateway'] <> "") 
 					$natrules .= filter_nat_rules_generate_if($optcfg['if'],
 						$lansa . "/" . $lancfg['subnet'], null, "", null, null, "");
-				}
 					
 				$natrules .= filter_nat_rules_generate_if($wanif,
 					$optsa . "/" . $optcfg['subnet'], null, "", null, null, "");