diff --git a/schema/xos-core.yang b/schema/xos-core.yang
index 82d1a7e..3de5ba3 100644
--- a/schema/xos-core.yang
+++ b/schema/xos-core.yang
@@ -41,9 +41,9 @@
   typedef unique-identifier {
     description "defines valid formats for external reference id";
     type union {
+      type uint32 { range 1..max; }
       type yang:uuid;
       type inet:uri;
-      type uint32 { range 1..max; }
     }
   }