diff --git a/lib/util/resolve-local-ref.js b/lib/util/resolve-local-ref.js
index ca6aea80..edf406db 100644
--- a/lib/util/resolve-local-ref.js
+++ b/lib/util/resolve-local-ref.js
@@ -24,10 +24,7 @@ function resolveLocalRef (jsonSchema, externalSchemas) {
   // for oneOf, anyOf, allOf support in querystring/params/headers
   if (jsonSchema.oneOf || jsonSchema.anyOf || jsonSchema.allOf) {
     const schemas = jsonSchema.oneOf || jsonSchema.anyOf || jsonSchema.allOf
-    return schemas.reduce(function (acc, schema) {
-      const json = resolveLocalRef(schema, externalSchemas)
-      return { ...acc, ...json }
-    }, {})
+    return schemas.reduce((acc, schema) => Object.assign(acc, resolveLocalRef(schema, externalSchemas)), {})
   }
 
   // $ref is in the format: #/definitions/<resolved definition>/<optional fragment>