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
@@ -195,6 +195,33 @@
     .flat();
 }
 
+function discardKeyserverUsernames(
+  newUserInfos: UserInfos,
+  stateUserInfos: UserInfos,
+): UserInfos {
+  let result: UserInfos = {};
+  for (const id in newUserInfos) {
+    if (stateUserInfos[id]) {
+      result = {
+        ...result,
+        [id]: {
+          ...newUserInfos[id],
+          username: stateUserInfos[id].username,
+        },
+      };
+    } else {
+      result = {
+        ...result,
+        [id]: {
+          ...newUserInfos[id],
+          username: null,
+        },
+      };
+    }
+  }
+  return result;
+}
+
 function reduceUserInfos(
   state: UserStore,
   action: BaseAction,
@@ -248,10 +275,15 @@
     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(