diff --git a/src/opnsense/mvc/app/library/OPNsense/Firewall/SNatRule.php b/src/opnsense/mvc/app/library/OPNsense/Firewall/SNatRule.php
index f7ead8831..3eca19d6a 100644
--- a/src/opnsense/mvc/app/library/OPNsense/Firewall/SNatRule.php
+++ b/src/opnsense/mvc/app/library/OPNsense/Firewall/SNatRule.php
@@ -98,12 +98,12 @@ class SNatRule extends Rule
             }
             foreach (array("sourceport", "dstport", "natport") as $fieldname) {
                 if (!empty($rule[$fieldname]) && Util::isAlias($rule[$fieldname])) {
-                    $rule[$fieldname] = "$".$rule[$fieldname];
                     if (!Util::isAlias($rule[$fieldname], true)) {
                         // unable to map port
                         $this->log("SNAT / unable to map port ". $rule[$fieldname]. ", empty?");
                         $rule['disabled'] = true;
                     }
+                    $rule[$fieldname] = "$".$rule[$fieldname];
                 }
             }
             if (!empty($rule['staticnatport']) || !empty($rule['nonat'])) {