diff --git a/plugins/chunter/src/index.ts b/plugins/chunter/src/index.ts
index 99a73c3025..d65e981351 100644
--- a/plugins/chunter/src/index.ts
+++ b/plugins/chunter/src/index.ts
@@ -45,6 +45,16 @@ export interface Backlink extends Comment {
   backlinkClass: Ref<Class<Doc>>
 }
 
+/**
+ * @public
+ */
+export interface Attachment extends Doc {
+  attachmentTo: Ref<Doc>
+  collection: string
+  name: string
+  file: string
+}
+
 /**
  * @public
  */
@@ -59,7 +69,8 @@ export default plugin(chunterId, {
   class: {
     Message: '' as Ref<Class<Message>>,
     Backlink: '' as Ref<Class<Backlink>>,
-    Comment: '' as Ref<Class<Comment>>
+    Comment: '' as Ref<Class<Comment>>,
+    Attachment: '' as Ref<Class<Attachment>>
   },
   space: {
     Backlinks: '' as Ref<Space>