diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/directory.go b/src/github.com/matrix-org/dendrite/clientapi/routing/directory.go
index d5df2dd2d..e7f4ef2a6 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/directory.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/directory.go
@@ -116,14 +116,12 @@ func SetLocalAlias(
 	// Check that the alias does not fall within an exclusive namespace of an
 	// application service
 	for _, appservice := range cfg.Derived.ApplicationServices {
-		for key, namespaceMaps := range appservice.NamespaceMap {
-			if key == "aliases" {
-				for _, namespace := range namespaceMaps {
-					if namespace.Exclusive && namespace.RegexpObject.MatchString(alias) {
-						return util.JSONResponse{
-							Code: http.StatusBadRequest,
-							JSON: jsonerror.ASExclusive("Alias is reserved by an application service"),
-						}
+		if userNamespaces, ok := appservice.NamespaceMap["users"]; ok {
+			for _, namespace := range userNamespaces {
+				if namespace.Exclusive && namespace.RegexpObject.MatchString(alias) {
+					return util.JSONResponse{
+						Code: http.StatusBadRequest,
+						JSON: jsonerror.ASExclusive("Alias is reserved by an application service"),
 					}
 				}
 			}