diff --git a/lib/serializer-compiler.js b/lib/serializer-compiler.js
index 9d1298c..4b54f3e 100644
--- a/lib/serializer-compiler.js
+++ b/lib/serializer-compiler.js
@@ -5,7 +5,7 @@ const AjvJTD = require('ajv/dist/jtd')
 const defaultAjvOptions = require('./default-ajv-options')
 
 class SerializerCompiler {
-  constructor (externalSchemas, options) {
+  constructor (_externalSchemas, options) {
     this.ajv = new AjvJTD(Object.assign({}, defaultAjvOptions, options))
 
     /**