diff --git a/imageroot/actions/configure-module/validate-input.json b/imageroot/actions/configure-module/validate-input.json
index 2b85858..5bc564c 100644
--- a/imageroot/actions/configure-module/validate-input.json
+++ b/imageroot/actions/configure-module/validate-input.json
@@ -37,7 +37,7 @@
         "domain": {
             "type": "string",
             "title": "Domain name",
-            "pattern": "^[a-zA-Z][-a-zA-Z0-9]{0,62}(\\.[a-zA-Z][-a-zA-Z0-9]{0,62})+$",
+            "pattern": "^[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(\\.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+$",
             "maxLength": 140,
             "minLength": 1
         }