diff --git a/schemas/legacy.json b/schemas/legacy.json
index aded4d3..3a424a3 100644
--- a/schemas/legacy.json
+++ b/schemas/legacy.json
@@ -1010,7 +1010,9 @@
                 "enum": ["Low"]
             },
             "Index": {
-                "type": "number"
+                "type": "number",
+                "minimum": 0,
+                "multipleOf": 1
             },
             "InScaleFactor": {
                 "type": "number"