diff --git a/packages/netlify-cms-core/src/components/Editor/EditorControlPane/Widget.js b/packages/netlify-cms-core/src/components/Editor/EditorControlPane/Widget.js
index c05de96d..0ee846c9 100644
--- a/packages/netlify-cms-core/src/components/Editor/EditorControlPane/Widget.js
+++ b/packages/netlify-cms-core/src/components/Editor/EditorControlPane/Widget.js
@@ -132,6 +132,9 @@ export default class Widget extends Component {
       return { error: false };
     }
 
+    // Convert list input widget value to string for pattern test
+    List.isList(value) && (value = value.join(','));
+
     if (pattern && !RegExp(pattern.first()).test(value)) {
       const error = {
         type: ValidationErrorTypes.PATTERN,