diff --git a/src/components/progress_button/progress_button.vue b/src/components/progress_button/progress_button.vue
index 3fea241818..737360bbf6 100644
--- a/src/components/progress_button/progress_button.vue
+++ b/src/components/progress_button/progress_button.vue
@@ -15,7 +15,7 @@ export default {
     disabled: {
       type: Boolean
     },
-    click: {
+    click: { // click event handler. Must return a promise
       type: Function,
       default: () => Promise.resolve()
     }