diff --git a/source/structure/r1.sindri.json b/source/structure/r1.sindri.json
index e757245..7ec6440 100644
--- a/source/structure/r1.sindri.json
+++ b/source/structure/r1.sindri.json
@@ -138,6 +138,12 @@
 				}
 			],
 			"constraints": [
+				{
+					"kind": "unique",
+					"parameters": {
+						"fields": ["kind","sub_id"]
+					}
+				}
 			]
 		},
 		{