diff --git a/modules/openapi-generator/src/main/resources/Javascript/es6/partial_model_generic.mustache b/modules/openapi-generator/src/main/resources/Javascript/es6/partial_model_generic.mustache
index 398194c0c64e..cc82b99becbd 100644
--- a/modules/openapi-generator/src/main/resources/Javascript/es6/partial_model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/Javascript/es6/partial_model_generic.mustache
@@ -26,7 +26,7 @@ class {{classname}} {{#parent}}{{^parentModel}}{{#vendorExtensions.x-is-array}}e
      * Only for internal use.
      */{{/emitJSDoc}}
     static initialize(obj{{#vendorExtensions.x-all-required}}, {{name}}{{/vendorExtensions.x-all-required}}) { {{#vars}}{{#required}}
-        obj['{{baseName}}'] = {{name}};{{/required}}{{/vars}}
+        {{#defaultValue}}obj['{{baseName}}'] = {{name}} || {{{defaultValue}}};{{/defaultValue}}{{^defaultValue}}obj['{{baseName}}'] = {{name}};{{/defaultValue}}{{/required}}{{/vars}}
     }
 
     {{#emitJSDoc}}/**
diff --git a/modules/openapi-generator/src/main/resources/Javascript/partial_model_generic.mustache b/modules/openapi-generator/src/main/resources/Javascript/partial_model_generic.mustache
index 8531f93ae001..e6fcc62c9e3c 100644
--- a/modules/openapi-generator/src/main/resources/Javascript/partial_model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/Javascript/partial_model_generic.mustache
@@ -33,7 +33,12 @@
     {{/useInheritance}}
     {{#vars}}
     {{#required}}
+    {{#defaultValue}}
+    _this['{{baseName}}'] = {{name}} || {{{defaultValue}}};
+    {{/defaultValue}}
+    {{^defaultValue}}
     _this['{{baseName}}'] = {{name}};
+    {{/defaultValue}}
     {{/required}}
     {{/vars}}
     {{#parent}}
diff --git a/samples/client/petstore/javascript-es6/src/model/Category.js b/samples/client/petstore/javascript-es6/src/model/Category.js
index 00d86502a632..557e8e186206 100644
--- a/samples/client/petstore/javascript-es6/src/model/Category.js
+++ b/samples/client/petstore/javascript-es6/src/model/Category.js
@@ -35,7 +35,7 @@ class Category {
      * Only for internal use.
      */
     static initialize(obj, name) { 
-        obj['name'] = name;
+        obj['name'] = name || 'default-name';
     }
 
     /**
diff --git a/samples/client/petstore/javascript-promise-es6/src/model/Category.js b/samples/client/petstore/javascript-promise-es6/src/model/Category.js
index 00d86502a632..557e8e186206 100644
--- a/samples/client/petstore/javascript-promise-es6/src/model/Category.js
+++ b/samples/client/petstore/javascript-promise-es6/src/model/Category.js
@@ -35,7 +35,7 @@ class Category {
      * Only for internal use.
      */
     static initialize(obj, name) { 
-        obj['name'] = name;
+        obj['name'] = name || 'default-name';
     }
 
     /**