diff --git a/lib/types/thread-types.js b/lib/types/thread-types.js
--- a/lib/types/thread-types.js
+++ b/lib/types/thread-types.js
@@ -2,7 +2,7 @@
 
 import invariant from 'invariant';
 
-import type { ClientAvatar } from './avatar-types.js';
+import type { ClientAvatar, UpdateUserAvatarRequest } from './avatar-types.js';
 import type { Shape } from './core.js';
 import type { CalendarQuery, RawEntryInfo } from './entry-types.js';
 import type { Media } from './media-types.js';
@@ -384,6 +384,7 @@
   +color: string,
   +parentThreadID: ?string,
   +newMemberIDs: $ReadOnlyArray<string>,
+  +avatar: UpdateUserAvatarRequest,
 }>;
 
 export type UpdateThreadRequest = {