diff --git a/src/models/timelines.rs b/src/models/timelines.rs
index 96d78dfa..6a7e502d 100644
--- a/src/models/timelines.rs
+++ b/src/models/timelines.rs
@@ -90,7 +90,7 @@ pub struct TimelineEvent {
 pub struct DismissedReview {
     state: pulls::ReviewState,
     review_id: ReviewId,
-    dismissal_message: String,
+    dismissal_message: Option<String>,
     dismissal_commit_id: Option<String>,
 }