diff --git a/crates/matrix-sdk-base/src/deserialized_responses.rs b/crates/matrix-sdk-base/src/deserialized_responses.rs
index 9785e33d6..c37a664ac 100644
--- a/crates/matrix-sdk-base/src/deserialized_responses.rs
+++ b/crates/matrix-sdk-base/src/deserialized_responses.rs
@@ -34,9 +34,12 @@ use serde::Serialize;
 
 /// A change in ambiguity of room members that an `m.room.member` event
 /// triggers.
-#[derive(Clone, Debug, Default)]
+#[derive(Clone, Debug)]
 #[non_exhaustive]
 pub struct AmbiguityChange {
+    /// The user ID of the member that is contained in the state key of the
+    /// `m.room.member` event.
+    pub member_id: OwnedUserId,
     /// Is the member that is contained in the state key of the `m.room.member`
     /// event itself ambiguous because of the event.
     pub member_ambiguous: bool,
diff --git a/crates/matrix-sdk-base/src/store/ambiguity_map.rs b/crates/matrix-sdk-base/src/store/ambiguity_map.rs
index 6cded30c2..25ce7366e 100644
--- a/crates/matrix-sdk-base/src/store/ambiguity_map.rs
+++ b/crates/matrix-sdk-base/src/store/ambiguity_map.rs
@@ -118,6 +118,7 @@ impl AmbiguityCache {
         self.update(room_id, old_map, new_map);
 
         let change = AmbiguityChange {
+            member_id: member_event.state_key().clone(),
             disambiguated_member,
             ambiguated_member,
             member_ambiguous: ambiguous,