diff --git a/lib/utils/user-info-extraction-utils.js b/lib/utils/user-info-extraction-utils.js
--- a/lib/utils/user-info-extraction-utils.js
+++ b/lib/utils/user-info-extraction-utils.js
@@ -61,6 +61,8 @@
   } else if (inputValidator.meta.kind === 'maybe') {
     const typeObj = extendResponderValidatorBase(inputValidator.meta.type);
     return (t.maybe(typeObj): any);
+  } else if (inputValidator.meta.kind === 'subtype') {
+    return extendResponderValidatorBase(inputValidator.meta.type);
   }
 
   return inputValidator;