diff --git a/jsonschema/src/main/scala/pl/iterators/kebs/jsonschema/KebsJsonSchemaPredefs.scala b/jsonschema/src/main/scala/pl/iterators/kebs/jsonschema/KebsJsonSchemaPredefs.scala
index 6c9f6b19..6683060d 100644
--- a/jsonschema/src/main/scala/pl/iterators/kebs/jsonschema/KebsJsonSchemaPredefs.scala
+++ b/jsonschema/src/main/scala/pl/iterators/kebs/jsonschema/KebsJsonSchemaPredefs.scala
@@ -3,11 +3,13 @@ package pl.iterators.kebs.jsonschema
 import json.schema.Predef
 
 import java.net.{URI, URL}
-import java.time.ZonedDateTime
+import java.time.{YearMonth, ZonedDateTime}
 
 trait KebsJsonSchemaPredefs {
   implicit val predefZonedDateTime: Predef[ZonedDateTime] = Predef(json.Schema.`string`[ZonedDateTime])
 
+  implicit val predefYearMonth: Predef[YearMonth] = Predef(json.Schema.`string`[YearMonth])
+
   implicit val predefUrl: Predef[URL] = Predef(json.Schema.`string`[URL])
 
   implicit val predefUri: Predef[URI] = Predef(json.Schema.`string`[URI])