diff --git a/ruma-client-api/CHANGELOG.md b/ruma-client-api/CHANGELOG.md
index 205548dc..9030e067 100644
--- a/ruma-client-api/CHANGELOG.md
+++ b/ruma-client-api/CHANGELOG.md
@@ -16,6 +16,7 @@ Breaking changes:
   `Ruleset` type from `ruma_common::push` (also available as `ruma::push`)
 * Fix event types in `r0::context::get_context`
 * Fix event types in `r0::sync::sync_events`
+* Update type of `user_id` in `r0::account::whoami` from `String` to `ruma_identifiers::UserId`
 
 Improvements:
 
diff --git a/ruma-client-api/src/r0/account/whoami.rs b/ruma-client-api/src/r0/account/whoami.rs
index cee6c52a..cdc2b7e7 100644
--- a/ruma-client-api/src/r0/account/whoami.rs
+++ b/ruma-client-api/src/r0/account/whoami.rs
@@ -1,6 +1,7 @@
 //! [GET /_matrix/client/r0/account/whoami](https://matrix.org/docs/spec/client_server/r0.6.0#get-matrix-client-r0-account-whoami)
 
 use ruma_api::ruma_api;
+use ruma_identifiers::UserId;
 
 ruma_api! {
     metadata {
@@ -16,7 +17,7 @@ ruma_api! {
 
     response {
         /// The id of the user that owns the access token.
-        pub user_id: String,
+        pub user_id: UserId,
     }
 
     error: crate::Error