diff --git a/addons/knobs/src/components/types/Array.tsx b/addons/knobs/src/components/types/Array.tsx
index fb360866712..3b1bed3bb30 100644
--- a/addons/knobs/src/components/types/Array.tsx
+++ b/addons/knobs/src/components/types/Array.tsx
@@ -62,7 +62,7 @@ export default class ArrayType extends Component<ArrayTypeProps> {
 
   render() {
     const { knob } = this.props;
-    const value = knob.value.join(knob.separator);
+    const value = knob.value && knob.value.join(knob.separator);
 
     return (
       <Form.Textarea