diff --git a/schemas/osbuild2.json b/schemas/osbuild2.json
index 04645913..4e258810 100644
--- a/schemas/osbuild2.json
+++ b/schemas/osbuild2.json
@@ -18,8 +18,11 @@
 
     "inputs": {
       "title": "Collection of inputs for a stage",
-      "additionalProperties": {
-        "$ref": "#/definitions/input"
+      "additionalProperties": false,
+      "patternProperties": {
+        "^[a-zA-Z][a-zA-Z0-9_\\-\\.]{0,254}": {
+          "$ref": "#/definitions/input"
+        }
       }
     },