diff --git a/lib/selectors/socket-selectors.js b/lib/selectors/socket-selectors.js
--- a/lib/selectors/socket-selectors.js
+++ b/lib/selectors/socket-selectors.js
@@ -1,6 +1,7 @@
 // @flow
 
 import { createSelector } from 'reselect';
+import t from 'tcomb';
 
 import { currentCalendarQuery } from './nav-selectors.js';
 import {
@@ -10,7 +11,11 @@
 } from '../shared/entry-utils.js';
 import threadWatcher from '../shared/thread-watcher.js';
 import type { SignedIdentityKeysBlob } from '../types/crypto-types.js';
-import type { RawEntryInfo, CalendarQuery } from '../types/entry-types.js';
+import {
+  type RawEntryInfo,
+  rawEntryInfoValidator,
+  type CalendarQuery,
+} from '../types/entry-types.js';
 import type { AppState } from '../types/redux-types.js';
 import type { ClientReportCreationRequest } from '../types/report-types.js';
 import {
@@ -20,11 +25,25 @@
 } from '../types/request-types.js';
 import type { SessionState } from '../types/session-types.js';
 import type { OneTimeKeyGenerator } from '../types/socket-types.js';
-import type { RawThreadInfo } from '../types/thread-types.js';
-import type { CurrentUserInfo, UserInfos } from '../types/user-types.js';
+import {
+  type RawThreadInfo,
+  rawThreadInfoValidator,
+} from '../types/thread-types.js';
+import {
+  type CurrentUserInfo,
+  currentUserInfoValidator,
+  type UserInfos,
+  userInfosValidator,
+} from '../types/user-types.js';
 import { getConfig } from '../utils/config.js';
 import { minimumOneTimeKeysRequired } from '../utils/crypto-utils.js';
 import { values, hash } from '../utils/objects.js';
+import {
+  tID,
+  convertClientIDsToServerIDs,
+  keyserverPrefixID,
+  convertToNewIDSchema,
+} from '../utils/validation-utils.js';
 
 const queuedReports: (
   state: AppState,
@@ -80,10 +99,34 @@
             platformDetails: getConfig().platformDetails,
           });
         } else if (serverRequest.type === serverRequestTypes.CHECK_STATE) {
-          const filteredEntryInfos = filterRawEntryInfosByCalendarQuery(
+          let filteredEntryInfos = filterRawEntryInfosByCalendarQuery(
             serverEntryInfosObject(values(entryInfos)),
             calendarQuery(calendarActive),
           );
+
+          if (convertToNewIDSchema) {
+            threadInfos = convertClientIDsToServerIDs(
+              keyserverPrefixID,
+              t.dict(tID, rawThreadInfoValidator),
+              threadInfos,
+            );
+            userInfos = convertClientIDsToServerIDs(
+              keyserverPrefixID,
+              userInfosValidator,
+              userInfos,
+            );
+            currentUserInfo = convertClientIDsToServerIDs(
+              keyserverPrefixID,
+              t.maybe(currentUserInfoValidator),
+              currentUserInfo,
+            );
+            filteredEntryInfos = convertClientIDsToServerIDs(
+              keyserverPrefixID,
+              t.dict(tID, rawEntryInfoValidator),
+              filteredEntryInfos,
+            );
+          }
+
           const hashResults = {};
           for (const key in serverRequest.hashesToCheck) {
             const expectedHashValue = serverRequest.hashesToCheck[key];