diff --git a/include/rapidjson/schema.h b/include/rapidjson/schema.h
index d88406443..2713fb260 100644
--- a/include/rapidjson/schema.h
+++ b/include/rapidjson/schema.h
@@ -355,6 +355,7 @@ class Schema {
         not_(),
         type_((1 << kTotalSchemaType) - 1), // typeless
         validatorCount_(),
+        notValidatorIndex_(),
         properties_(),
         additionalPropertiesSchema_(),
         patternProperties_(),