diff --git a/lib/reducers/user-reducer.js b/lib/reducers/user-reducer.js
--- a/lib/reducers/user-reducer.js
+++ b/lib/reducers/user-reducer.js
@@ -224,6 +224,24 @@
     .flat();
 }
 
+function discardKeyserverUsernames(
+  newUserInfos: UserInfos,
+  stateUserInfos: UserInfos,
+): UserInfos {
+  let result: UserInfos = {};
+  for (const id in newUserInfos) {
+    const username = stateUserInfos[id] ? stateUserInfos[id].username : null;
+    result = {
+      ...result,
+      [id]: {
+        ...newUserInfos[id],
+        username,
+      },
+    };
+  }
+  return result;
+}
+
 type ReduceUserInfosResult = [
   UserStore,
   $ReadOnlyArray<ClientUserInconsistencyReportCreationRequest>,
@@ -314,10 +332,15 @@
     if (keyserverID !== authoritativeKeyserverID()) {
       return [state, [], []];
     }
-    const newUserInfos: UserInfos = _keyBy(userInfo => userInfo.id)(
+    const keyserverUserInfos: UserInfos = _keyBy(userInfo => userInfo.id)(
       action.payload.userInfos,
     );
 
+    const newUserInfos = discardKeyserverUsernames(
+      keyserverUserInfos,
+      state.userInfos,
+    );
+
     const userStoreOps: $ReadOnlyArray<UserStoreOperation> =
       convertUserInfosToReplaceUserOps(newUserInfos);
     const processedUserInfos: UserInfos = processUserStoreOps(