diff --git a/ptypy/schema/ptypy_xmcd_calc_param.json b/ptypy/schema/ptypy_xmcd_calc_param.json
index f5ebdd7..cc05118 100644
--- a/ptypy/schema/ptypy_xmcd_calc_param.json
+++ b/ptypy/schema/ptypy_xmcd_calc_param.json
@@ -2,10 +2,12 @@
   "type": "object",
   "properties": {
     "scan_number_lcp": {
-      "type": "integer"
+      "type": "integer",
+      "minimum": "0"
     },
     "scan_number_rcp": {
-      "type": "integer"
+      "type": "integer",
+      "minimum": "0"
     },
     "input_dir": {
       "type": "string",
@@ -67,5 +69,24 @@
       "type": "integer",
       "default": "-1"
     }
-  }
+  },
+  "required": [
+    "scan_number_lcp",
+    "scan_number_rcp",
+    "input_dir",
+    "output_dir",
+    "crop",
+    "align_x1",
+    "align_x2",
+    "align_y1",
+    "align_y2",
+    "ramp_x1",
+    "ramp_x2",
+    "ramp_y1",
+    "ramp_y2",
+    "norm_x1",
+    "norm_x2",
+    "norm_y1",
+    "norm_y2"
+  ]
 }
\ No newline at end of file