diff --git a/src/java-type.js b/src/java-type.js
index 8539369..f1df59d 100644
--- a/src/java-type.js
+++ b/src/java-type.js
@@ -50,7 +50,7 @@ const SUPPORTED_TYPES = {
 }
 
 
-function getCustomType(type, namespace, suffix) {
+function getCustomType(type, namespace, suffix='') {
 
     let match = LAST_ELEMENT_REGEX.exec(type)
     let name = ''
@@ -84,7 +84,7 @@ function mapCollection(type) {
 }
 
 module.exports = {
-    mapJavaType: (type, namespace, suffix) => {
+    mapJavaType: (type, namespace, suffix='') => {
         const baseType = COLLECTION_REGEX.exec(type)[1]
         let javaType = SUPPORTED_TYPES[baseType] || getCustomType(baseType, namespace, suffix)