diff --git a/backend/canisters/online_users/CHANGELOG.md b/backend/canisters/online_users/CHANGELOG.md
index 47e9a8e9c9..514d87ef2e 100644
--- a/backend/canisters/online_users/CHANGELOG.md
+++ b/backend/canisters/online_users/CHANGELOG.md
@@ -9,6 +9,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 - Added `c2c_remove_user` to be called by the UserIndex ([#6179](https://github.com/open-chat-labs/open-chat/pull/6179))
 
+### Changed
+
+- Clear the principal to userId map to ensure latest values are used ([#6184](https://github.com/open-chat-labs/open-chat/pull/6184))
+
 ## [[2.0.1149](https://github.com/open-chat-labs/open-chat/releases/tag/v2.0.1149-online_users)] - 2024-04-23
 
 ### Changed
diff --git a/backend/canisters/online_users/impl/src/lifecycle/post_upgrade.rs b/backend/canisters/online_users/impl/src/lifecycle/post_upgrade.rs
index 7ba1c36fda..a434762fb0 100644
--- a/backend/canisters/online_users/impl/src/lifecycle/post_upgrade.rs
+++ b/backend/canisters/online_users/impl/src/lifecycle/post_upgrade.rs
@@ -1,6 +1,6 @@
 use crate::lifecycle::{init_env, init_state};
 use crate::memory::get_upgrades_memory;
-use crate::Data;
+use crate::{mutate_state, Data};
 use canister_logger::LogEntry;
 use canister_tracing_macros::trace;
 use ic_cdk::post_upgrade;
@@ -24,4 +24,7 @@ fn post_upgrade(args: Args) {
     init_state(env, data, args.wasm_version);
 
     info!(version = %args.wasm_version, "Post-upgrade complete");
+
+    // TODO remove this after upgrade
+    mutate_state(|state| state.data.principal_to_user_id_map.clear());
 }
diff --git a/backend/canisters/online_users/impl/src/model/principal_to_user_id_map.rs b/backend/canisters/online_users/impl/src/model/principal_to_user_id_map.rs
index 8ca331ceeb..ac3b13fe16 100644
--- a/backend/canisters/online_users/impl/src/model/principal_to_user_id_map.rs
+++ b/backend/canisters/online_users/impl/src/model/principal_to_user_id_map.rs
@@ -22,6 +22,10 @@ impl PrincipalToUserIdMap {
     pub fn remove(&mut self, principal: &Principal) -> Option<UserId> {
         self.map.remove(principal).map(|u| u.into())
     }
+
+    pub fn clear(&mut self) {
+        self.map.clear_new()
+    }
 }
 
 fn init_map() -> StableBTreeMap<Principal, Principal, Memory> {