diff --git a/setup/config/config_appservice.go b/setup/config/config_appservice.go
index 4f6553f10..3f4e1c917 100644
--- a/setup/config/config_appservice.go
+++ b/setup/config/config_appservice.go
@@ -209,13 +209,14 @@ func setupRegexps(asAPI *AppServiceAPI, derived *Derived) (err error) {
 	for _, appservice := range derived.ApplicationServices {
 		// The sender_localpart can be considered an exclusive regex for a single user, so let's do that
 		// to simplify the code
-		var senderUserIDSlice = []string{fmt.Sprintf("@%s:%s", appservice.SenderLocalpart, asAPI.Matrix.ServerName)}
-		usersSlice, found := appservice.NamespaceMap["users"]
+		users, found := appservice.NamespaceMap["users"]
 		if !found {
-			usersSlice = []ApplicationServiceNamespace{}
-			appservice.NamespaceMap["users"] = usersSlice
+			users = []ApplicationServiceNamespace{}
 		}
-		appendExclusiveNamespaceRegexs(&senderUserIDSlice, usersSlice)
+		appservice.NamespaceMap["users"] = append(users, ApplicationServiceNamespace{
+			Exclusive: true,
+			Regex:     regexp.QuoteMeta(fmt.Sprintf("@%s:%s", appservice.SenderLocalpart, asAPI.Matrix.ServerName)),
+		})
 
 		for key, namespaceSlice := range appservice.NamespaceMap {
 			switch key {