diff --git a/ih/conf.py b/ih/conf.py
index d68508629a20e6a229c78a1aa05930407d87d76f..f67a197bf54035f832ea258d3336594da9311fe0 100644
--- a/ih/conf.py
+++ b/ih/conf.py
@@ -1205,9 +1205,8 @@ valid = {
                 "value": ""
             },
             "--thresh": {
-                "type": "string",
-                "validation": "list",
-                "value": ["binary", "inverse", "truncate", "tozero", "otsu"]
+                "type": "numeric",
+                "required": "true"
             },
             "--max": {
                 "type": "numeric",
@@ -1217,7 +1216,7 @@ valid = {
             "--type": {
                 "type": "string",
                 "validation": "list",
-                "value": ["binary", "trunc", "otsu", "tozero"]
+                "value": ["binary", "inverse", "trunc", "otsu", "tozero"]
             }
         }
     },