diff --git a/imageroot/actions/configure-module/validate-input.json b/imageroot/actions/configure-module/validate-input.json
index d19e577..06cfb23 100755
--- a/imageroot/actions/configure-module/validate-input.json
+++ b/imageroot/actions/configure-module/validate-input.json
@@ -26,7 +26,8 @@
         "host": {
             "type": "string",
             "description": "Host name for the application, like 'roundcubemail.domain.org'",
-            "format": "idn-hostname"
+            "format": "hostname",
+            "pattern": "\\."
         },
         "lets_encrypt": {
             "type": "boolean",