diff --git a/lib/handlers/peer-to-peer-message-handler.js b/lib/handlers/peer-to-peer-message-handler.js
index 2a6864bf8..dbf651cdf 100644
--- a/lib/handlers/peer-to-peer-message-handler.js
+++ b/lib/handlers/peer-to-peer-message-handler.js
@@ -1,119 +1,133 @@
 // @flow
 
 import type {
   IdentityServiceClient,
   DeviceOlmInboundKeys,
 } from '../types/identity-service-types.js';
 import {
   peerToPeerMessageTypes,
   type PeerToPeerMessage,
 } from '../types/tunnelbroker/peer-to-peer-message-types.js';
 import { getConfig } from '../utils/config.js';
 import { getContentSigningKey } from '../utils/crypto-utils.js';
 import { hasHigherDeviceID, olmSessionErrors } from '../utils/olm-utils.js';
 
 async function peerToPeerMessageHandler(
   message: PeerToPeerMessage,
   identityClient: IdentityServiceClient,
+  messageID: string,
 ): Promise<void> {
   const { olmAPI } = getConfig();
   if (message.type === peerToPeerMessageTypes.OUTBOUND_SESSION_CREATION) {
     const { senderInfo, encryptedData, sessionVersion } = message;
     const { userID: senderUserID, deviceID: senderDeviceID } = senderInfo;
 
     let deviceKeys: ?DeviceOlmInboundKeys = null;
     try {
       const { keys } = await identityClient.getInboundKeysForUser(senderUserID);
       deviceKeys = keys[senderDeviceID];
     } catch (e) {
       console.log(e.message);
     }
 
     if (!deviceKeys) {
       console.log(
         'Error creating inbound session with device ' +
           `${senderDeviceID}: No keys for the device, ` +
           `session version: ${sessionVersion}`,
       );
       return;
     }
 
     try {
       await olmAPI.initializeCryptoAccount();
       const result = await olmAPI.contentInboundSessionCreator(
         deviceKeys.identityKeysBlob.primaryIdentityPublicKeys,
         encryptedData,
         sessionVersion,
         false,
       );
       console.log(
         'Created inbound session with device ' +
           `${senderDeviceID}: ${result}, ` +
           `session version: ${sessionVersion}`,
       );
     } catch (e) {
       if (e.message?.includes(olmSessionErrors.alreadyCreated)) {
         console.log(
           'Received session request with lower session version from ' +
             `${senderDeviceID}, session version: ${sessionVersion}`,
         );
       } else if (e.message?.includes(olmSessionErrors.raceCondition)) {
         const currentDeviceID = await getContentSigningKey();
         if (hasHigherDeviceID(currentDeviceID, senderDeviceID)) {
           console.log(
             'Race condition while creating session with ' +
               `${senderDeviceID}, session version: ${sessionVersion}, ` +
               `this device has a higher deviceID and the session will be kept`,
           );
         } else {
           const result = await olmAPI.contentInboundSessionCreator(
             deviceKeys.identityKeysBlob.primaryIdentityPublicKeys,
             encryptedData,
             sessionVersion,
             true,
           );
           console.log(
             'Overwrite session with device ' +
               `${senderDeviceID}: ${result}, ` +
               `session version: ${sessionVersion}`,
           );
           // Resend all not-yet confirmed messages that were encrypted
           // with overwrite session. Tracked in ENG-6982.
         }
       } else {
         console.log(
           'Error creating inbound session with device ' +
             `${senderDeviceID}: ${e.message}, ` +
             `session version: ${sessionVersion}`,
         );
       }
     }
   } else if (message.type === peerToPeerMessageTypes.ENCRYPTED_MESSAGE) {
     try {
       await olmAPI.initializeCryptoAccount();
-      const decrypted = await olmAPI.decrypt(
+      const decrypted = await olmAPI.decryptSequential(
         message.encryptedData,
         message.senderInfo.deviceID,
+        messageID,
       );
       console.log(
         'Decrypted message from device ' +
           `${message.senderInfo.deviceID}: ${decrypted}`,
       );
     } catch (e) {
-      console.log(
-        'Error decrypting message from device ' +
-          `${message.senderInfo.deviceID}: ${e.message}`,
-      );
+      if (e.message?.includes(olmSessionErrors.messageAlreadyDecrypted)) {
+        console.log(
+          'Received already decrypted message from device ' +
+            `${message.senderInfo.deviceID}.`,
+        );
+      } else if (e.message?.includes(olmSessionErrors.messageOutOfOrder)) {
+        console.log(
+          'Received out-of-order message from device ' +
+            `${message.senderInfo.deviceID}.`,
+        );
+      } else {
+        console.log(
+          'Error decrypting message from device ' +
+            `${message.senderInfo.deviceID}: ${e.message}`,
+        );
+      }
     }
   } else if (message.type === peerToPeerMessageTypes.REFRESH_KEY_REQUEST) {
     try {
       await olmAPI.initializeCryptoAccount();
       const oneTimeKeys = await olmAPI.getOneTimeKeys(message.numberOfKeys);
       await identityClient.uploadOneTimeKeys(oneTimeKeys);
     } catch (e) {
       console.log(`Error uploading one-time keys: ${e.message}`);
     }
   }
 }
 
 export { peerToPeerMessageHandler };
diff --git a/lib/tunnelbroker/tunnelbroker-context.js b/lib/tunnelbroker/tunnelbroker-context.js
index 5e351f380..0573ca19d 100644
--- a/lib/tunnelbroker/tunnelbroker-context.js
+++ b/lib/tunnelbroker/tunnelbroker-context.js
@@ -1,443 +1,447 @@
 // @flow
 
 import invariant from 'invariant';
 import _isEqual from 'lodash/fp/isEqual.js';
 import * as React from 'react';
 import uuid from 'uuid';
 
 import type { SecondaryTunnelbrokerConnection } from './secondary-tunnelbroker-connection.js';
 import { tunnnelbrokerURL } from '../facts/tunnelbroker.js';
 import { peerToPeerMessageHandler } from '../handlers/peer-to-peer-message-handler.js';
 import { IdentityClientContext } from '../shared/identity-client-context.js';
 import { tunnelbrokerHeartbeatTimeout } from '../shared/timeouts.js';
 import { isWebPlatform } from '../types/device-types.js';
 import type { MessageReceiveConfirmation } from '../types/tunnelbroker/message-receive-confirmation-types.js';
 import type { MessageSentStatus } from '../types/tunnelbroker/message-to-device-request-status-types.js';
 import type { MessageToDeviceRequest } from '../types/tunnelbroker/message-to-device-request-types.js';
 import {
   type TunnelbrokerMessage,
   tunnelbrokerMessageTypes,
   tunnelbrokerMessageValidator,
 } from '../types/tunnelbroker/messages.js';
 import {
   type PeerToPeerMessage,
   peerToPeerMessageValidator,
 } from '../types/tunnelbroker/peer-to-peer-message-types.js';
 import type {
   AnonymousInitializationMessage,
   ConnectionInitializationMessage,
   TunnelbrokerInitializationMessage,
   TunnelbrokerDeviceTypes,
 } from '../types/tunnelbroker/session-types.js';
 import type { Heartbeat } from '../types/websocket/heartbeat-types.js';
 import { getConfig } from '../utils/config.js';
 import { getContentSigningKey } from '../utils/crypto-utils.js';
 import { useSelector } from '../utils/redux-utils.js';
 
 export type ClientMessageToDevice = {
   +deviceID: string,
   +payload: string,
 };
 
 export type TunnelbrokerSocketListener = (
   message: TunnelbrokerMessage,
 ) => mixed;
 
 type PromiseCallbacks = {
   +resolve: () => void,
   +reject: (error: string) => void,
 };
 type Promises = { [clientMessageID: string]: PromiseCallbacks };
 
 type TunnelbrokerContextType = {
   +sendMessage: (message: ClientMessageToDevice) => Promise<void>,
   +addListener: (listener: TunnelbrokerSocketListener) => void,
   +removeListener: (listener: TunnelbrokerSocketListener) => void,
   +connected: boolean,
   +isAuthorized: boolean,
   +setUnauthorizedDeviceID: (unauthorizedDeviceID: ?string) => void,
 };
 
 const TunnelbrokerContext: React.Context<?TunnelbrokerContextType> =
   React.createContext<?TunnelbrokerContextType>();
 
 type Props = {
   +children: React.Node,
   +shouldBeClosed?: boolean,
   +onClose?: () => mixed,
   +secondaryTunnelbrokerConnection?: SecondaryTunnelbrokerConnection,
 };
 
 function getTunnelbrokerDeviceType(): TunnelbrokerDeviceTypes {
   return isWebPlatform(getConfig().platformDetails.platform) ? 'web' : 'mobile';
 }
 
 function createAnonymousInitMessage(
   deviceID: string,
 ): AnonymousInitializationMessage {
   return ({
     type: 'AnonymousInitializationMessage',
     deviceID,
     deviceType: getTunnelbrokerDeviceType(),
   }: AnonymousInitializationMessage);
 }
 
 function TunnelbrokerProvider(props: Props): React.Node {
   const { children, shouldBeClosed, onClose, secondaryTunnelbrokerConnection } =
     props;
 
   const accessToken = useSelector(state => state.commServicesAccessToken);
   const userID = useSelector(state => state.currentUserInfo?.id);
 
   const [unauthorizedDeviceID, setUnauthorizedDeviceID] =
     React.useState<?string>(null);
   const isAuthorized = !unauthorizedDeviceID;
 
   const createInitMessage = React.useCallback(async () => {
     if (shouldBeClosed) {
       return null;
     }
 
     if (unauthorizedDeviceID) {
       return createAnonymousInitMessage(unauthorizedDeviceID);
     }
 
     if (!accessToken || !userID) {
       return null;
     }
 
     const deviceID = await getContentSigningKey();
     if (!deviceID) {
       return null;
     }
     return ({
       type: 'ConnectionInitializationMessage',
       deviceID,
       accessToken,
       userID,
       deviceType: getTunnelbrokerDeviceType(),
     }: ConnectionInitializationMessage);
   }, [accessToken, shouldBeClosed, unauthorizedDeviceID, userID]);
 
   const previousInitMessage =
     React.useRef<?TunnelbrokerInitializationMessage>(null);
 
   const [connected, setConnected] = React.useState(false);
   const listeners = React.useRef<Set<TunnelbrokerSocketListener>>(new Set());
   const socket = React.useRef<?WebSocket>(null);
   const promises = React.useRef<Promises>({});
   const heartbeatTimeoutID = React.useRef<?TimeoutID>();
 
   const identityContext = React.useContext(IdentityClientContext);
   invariant(identityContext, 'Identity context should be set');
   const { identityClient } = identityContext;
 
   const stopHeartbeatTimeout = React.useCallback(() => {
     if (heartbeatTimeoutID.current) {
       clearTimeout(heartbeatTimeoutID.current);
       heartbeatTimeoutID.current = null;
     }
   }, []);
 
   const resetHeartbeatTimeout = React.useCallback(() => {
     stopHeartbeatTimeout();
     heartbeatTimeoutID.current = setTimeout(() => {
       socket.current?.close();
       setConnected(false);
     }, tunnelbrokerHeartbeatTimeout);
   }, [stopHeartbeatTimeout]);
 
   // determine if the socket is active (not closed or closing)
   const isSocketActive =
     socket.current?.readyState === WebSocket.OPEN ||
     socket.current?.readyState === WebSocket.CONNECTING;
 
   const connectionChangePromise = React.useRef<?Promise<void>>(null);
   // The Tunnelbroker connection can have 4 states:
   // - DISCONNECTED: isSocketActive = false, connected = false
   //   Should be in this state when initMessage is null
   // - CONNECTING: isSocketActive = true, connected = false
   //   This lasts until Tunnelbroker sends ConnectionInitializationResponse
   // - CONNECTED: isSocketActive = true, connected = true
   // - DISCONNECTING: isSocketActive = false, connected = true
   //   This lasts between socket.close() and socket.onclose()
   React.useEffect(() => {
     connectionChangePromise.current = (async () => {
       await connectionChangePromise.current;
       try {
         const initMessage = await createInitMessage();
         const initMessageChanged = !_isEqual(
           previousInitMessage.current,
           initMessage,
         );
         previousInitMessage.current = initMessage;
 
         // when initMessage changes, we need to close the socket
         // and open a new one
         if (
           (!initMessage || initMessageChanged) &&
           isSocketActive &&
           socket.current
         ) {
           socket.current?.close();
           return;
         }
 
         // when we're already connected (or pending disconnection),
         // or there's no init message to start with, we don't need
         // to do anything
         if (connected || !initMessage || socket.current) {
           return;
         }
 
         const tunnelbrokerSocket = new WebSocket(tunnnelbrokerURL);
 
         tunnelbrokerSocket.onopen = () => {
           tunnelbrokerSocket.send(JSON.stringify(initMessage));
         };
 
         tunnelbrokerSocket.onclose = () => {
           // this triggers the effect hook again and reconnect
           setConnected(false);
           onClose?.();
           socket.current = null;
           console.log('Connection to Tunnelbroker closed');
         };
         tunnelbrokerSocket.onerror = e => {
           console.log('Tunnelbroker socket error:', e.message);
         };
         tunnelbrokerSocket.onmessage = (event: MessageEvent) => {
           if (typeof event.data !== 'string') {
             console.log('socket received a non-string message');
             return;
           }
           let rawMessage;
           try {
             rawMessage = JSON.parse(event.data);
           } catch (e) {
             console.log('error while parsing Tunnelbroker message:', e.message);
             return;
           }
 
           if (!tunnelbrokerMessageValidator.is(rawMessage)) {
             console.log('invalid TunnelbrokerMessage');
             return;
           }
           const message: TunnelbrokerMessage = rawMessage;
 
           resetHeartbeatTimeout();
 
           for (const listener of listeners.current) {
             listener(message);
           }
 
           if (
             message.type ===
             tunnelbrokerMessageTypes.CONNECTION_INITIALIZATION_RESPONSE
           ) {
             if (message.status.type === 'Success' && !connected) {
               setConnected(true);
               console.log(
                 'session with Tunnelbroker created. isAuthorized:',
                 isAuthorized,
               );
             } else if (message.status.type === 'Success' && connected) {
               console.log(
                 'received ConnectionInitializationResponse with status: Success for already connected socket',
               );
             } else {
               setConnected(false);
               console.log(
                 'creating session with Tunnelbroker error:',
                 message.status.data,
               );
             }
           } else if (
             message.type === tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE
           ) {
             const confirmation: MessageReceiveConfirmation = {
               type: tunnelbrokerMessageTypes.MESSAGE_RECEIVE_CONFIRMATION,
               messageIDs: [message.messageID],
             };
             socket.current?.send(JSON.stringify(confirmation));
 
             let rawPeerToPeerMessage;
             try {
               rawPeerToPeerMessage = JSON.parse(message.payload);
             } catch (e) {
               console.log(
                 'error while parsing Tunnelbroker peer-to-peer message:',
                 e.message,
               );
               return;
             }
 
             if (!peerToPeerMessageValidator.is(rawPeerToPeerMessage)) {
               console.log('invalid Tunnelbroker PeerToPeerMessage');
               return;
             }
             const peerToPeerMessage: PeerToPeerMessage = rawPeerToPeerMessage;
-            void peerToPeerMessageHandler(peerToPeerMessage, identityClient);
+            void peerToPeerMessageHandler(
+              peerToPeerMessage,
+              identityClient,
+              message.messageID,
+            );
           } else if (
             message.type ===
             tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE_REQUEST_STATUS
           ) {
             for (const status: MessageSentStatus of message.clientMessageIDs) {
               if (status.type === 'Success') {
                 promises.current[status.data]?.resolve();
                 delete promises.current[status.data];
               } else if (status.type === 'Error') {
                 promises.current[status.data.id]?.reject(status.data.error);
                 delete promises.current[status.data.id];
               } else if (status.type === 'SerializationError') {
                 console.log('SerializationError for message: ', status.data);
               } else if (status.type === 'InvalidRequest') {
                 console.log('Tunnelbroker recorded InvalidRequest');
               }
             }
           } else if (message.type === tunnelbrokerMessageTypes.HEARTBEAT) {
             const heartbeat: Heartbeat = {
               type: tunnelbrokerMessageTypes.HEARTBEAT,
             };
             socket.current?.send(JSON.stringify(heartbeat));
           }
         };
 
         socket.current = tunnelbrokerSocket;
       } catch (err) {
         console.log('Tunnelbroker connection error:', err);
       }
     })();
   }, [
     connected,
     isSocketActive,
     isAuthorized,
     resetHeartbeatTimeout,
     stopHeartbeatTimeout,
     identityClient,
     onClose,
     createInitMessage,
   ]);
 
   const sendMessageToDeviceRequest: (
     request: MessageToDeviceRequest,
   ) => Promise<void> = React.useCallback(
     request => {
       return new Promise((resolve, reject) => {
         const socketActive = connected && socket.current;
         if (!shouldBeClosed && !socketActive) {
           throw new Error('Tunnelbroker not connected');
         }
         promises.current[request.clientMessageID] = {
           resolve,
           reject,
         };
         if (socketActive) {
           socket.current?.send(JSON.stringify(request));
         } else {
           secondaryTunnelbrokerConnection?.sendMessage(request);
         }
       });
     },
     [connected, secondaryTunnelbrokerConnection, shouldBeClosed],
   );
 
   const sendMessage: (message: ClientMessageToDevice) => Promise<void> =
     React.useCallback(
       (message: ClientMessageToDevice) => {
         const clientMessageID = uuid.v4();
         const messageToDevice: MessageToDeviceRequest = {
           type: tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE_REQUEST,
           clientMessageID,
           deviceID: message.deviceID,
           payload: message.payload,
         };
 
         return sendMessageToDeviceRequest(messageToDevice);
       },
       [sendMessageToDeviceRequest],
     );
 
   React.useEffect(
     () =>
       secondaryTunnelbrokerConnection?.onSendMessage(message => {
         if (shouldBeClosed) {
           // We aren't supposed to be handling it
           return;
         }
 
         void (async () => {
           try {
             await sendMessageToDeviceRequest(message);
             secondaryTunnelbrokerConnection.setMessageStatus(
               message.clientMessageID,
             );
           } catch (error) {
             secondaryTunnelbrokerConnection.setMessageStatus(
               message.clientMessageID,
               error,
             );
           }
         })();
       }),
     [
       secondaryTunnelbrokerConnection,
       sendMessageToDeviceRequest,
       shouldBeClosed,
     ],
   );
 
   React.useEffect(
     () =>
       secondaryTunnelbrokerConnection?.onMessageStatus((messageID, error) => {
         if (error) {
           promises.current[messageID].reject(error);
         } else {
           promises.current[messageID].resolve();
         }
         delete promises.current[messageID];
       }),
     [secondaryTunnelbrokerConnection],
   );
 
   const addListener = React.useCallback(
     (listener: TunnelbrokerSocketListener) => {
       listeners.current.add(listener);
     },
     [],
   );
 
   const removeListener = React.useCallback(
     (listener: TunnelbrokerSocketListener) => {
       listeners.current.delete(listener);
     },
     [],
   );
 
   const value: TunnelbrokerContextType = React.useMemo(
     () => ({
       sendMessage,
       connected,
       isAuthorized,
       addListener,
       removeListener,
       setUnauthorizedDeviceID,
     }),
     [addListener, connected, removeListener, sendMessage, isAuthorized],
   );
 
   return (
     <TunnelbrokerContext.Provider value={value}>
       {children}
     </TunnelbrokerContext.Provider>
   );
 }
 
 function useTunnelbroker(): TunnelbrokerContextType {
   const context = React.useContext(TunnelbrokerContext);
   invariant(context, 'TunnelbrokerContext not found');
 
   return context;
 }
 
 export { TunnelbrokerProvider, useTunnelbroker };
diff --git a/lib/utils/olm-utils.js b/lib/utils/olm-utils.js
index 9854b8e28..22f0e81e6 100644
--- a/lib/utils/olm-utils.js
+++ b/lib/utils/olm-utils.js
@@ -1,148 +1,154 @@
 // @flow
 
 import type { Account as OlmAccount } from '@commapp/olm';
 
 import {
   getOneTimeKeyValuesFromBlob,
   getPrekeyValueFromBlob,
 } from '../shared/crypto-utils.js';
 import { ONE_TIME_KEYS_NUMBER } from '../types/identity-service-types.js';
 
 const maxPublishedPrekeyAge = 30 * 24 * 60 * 60 * 1000;
 const maxOldPrekeyAge = 24 * 60 * 60 * 1000;
 
 type AccountKeysSet = {
   +identityKeys: string,
   +prekey: string,
   +prekeySignature: string,
   +oneTimeKeys: $ReadOnlyArray<string>,
 };
 
 type IdentityKeysAndPrekeys = {
   +identityKeys: string,
   +prekey: string,
   +prekeySignature: string,
 };
 
 function validateAccountPrekey(account: OlmAccount) {
   if (shouldRotatePrekey(account)) {
     account.generate_prekey();
   }
   if (shouldForgetPrekey(account)) {
     account.forget_old_prekey();
   }
 }
 
 function shouldRotatePrekey(account: OlmAccount): boolean {
   // Our fork of Olm only remembers two prekeys at a time.
   // If the new one hasn't been published, then the old one is still active.
   // In that scenario, we need to avoid rotating the prekey because it will
   // result in the old active prekey being discarded.
   if (account.unpublished_prekey()) {
     return false;
   }
 
   const currentDate = new Date();
   const lastPrekeyPublishDate = getLastPrekeyPublishTime(account);
 
   return (
     currentDate.getTime() - lastPrekeyPublishDate.getTime() >=
     maxPublishedPrekeyAge
   );
 }
 
 function shouldForgetPrekey(account: OlmAccount): boolean {
   // Our fork of Olm only remembers two prekeys at a time.
   // We have to hold onto the old one until the new one is published.
   if (account.unpublished_prekey()) {
     return false;
   }
 
   const currentDate = new Date();
   const lastPrekeyPublishDate = getLastPrekeyPublishTime(account);
 
   return (
     currentDate.getTime() - lastPrekeyPublishDate.getTime() >= maxOldPrekeyAge
   );
 }
 
 function getLastPrekeyPublishTime(account: OlmAccount): Date {
   const olmLastPrekeyPublishTime = account.last_prekey_publish_time();
 
   // Olm uses seconds, while the Date() constructor expects milliseconds.
   return new Date(olmLastPrekeyPublishTime * 1000);
 }
 
 function getAccountPrekeysSet(account: OlmAccount): {
   +prekey: string,
   +prekeySignature: ?string,
 } {
   const prekey = getPrekeyValueFromBlob(account.prekey());
   const prekeySignature = account.prekey_signature();
   return { prekey, prekeySignature };
 }
 
 function getAccountOneTimeKeys(
   account: OlmAccount,
   numberOfKeys: number = ONE_TIME_KEYS_NUMBER,
 ): $ReadOnlyArray<string> {
   let oneTimeKeys = getOneTimeKeyValuesFromBlob(account.one_time_keys());
   if (oneTimeKeys.length < numberOfKeys) {
     account.generate_one_time_keys(numberOfKeys - oneTimeKeys.length);
     oneTimeKeys = getOneTimeKeyValuesFromBlob(account.one_time_keys());
   }
   return oneTimeKeys;
 }
 
 function retrieveAccountKeysSet(account: OlmAccount): AccountKeysSet {
   const { identityKeys, prekey, prekeySignature } =
     retrieveIdentityKeysAndPrekeys(account);
   const oneTimeKeys = getAccountOneTimeKeys(account, ONE_TIME_KEYS_NUMBER);
   return { identityKeys, oneTimeKeys, prekey, prekeySignature };
 }
 
 function retrieveIdentityKeysAndPrekeys(
   account: OlmAccount,
 ): IdentityKeysAndPrekeys {
   const identityKeys = account.identity_keys();
 
   validateAccountPrekey(account);
   const { prekey, prekeySignature } = getAccountPrekeysSet(account);
 
   if (!prekeySignature || !prekey) {
     throw new Error('invalid_prekey');
   }
 
   return { identityKeys, prekey, prekeySignature };
 }
 
 const olmSessionErrors = Object.freeze({
   // Two clients send the session request to each other at the same time,
   // we choose which session to keep based on `deviceID`.
   raceCondition: 'OLM_SESSION_CREATION_RACE_CONDITION',
   // The client received a session request with a lower session version,
   // this request can be ignored.
   alreadyCreated: 'OLM_SESSION_ALREADY_CREATED',
+  // If using sequential decrypt this error means that message was decrypted.
+  // Otherwise, it could mean that the receiver chain advance beyond and the key
+  // to decrypt that message was discarded.
+  messageAlreadyDecrypted: 'OLM_ALREADY_DECRYPTED_OR_KEYS_SKIPPED',
+  // One or more messages were skipped.
+  messageOutOfOrder: 'OLM_MESSAGE_OUT_OF_ORDER',
 });
 
 function hasHigherDeviceID(
   currenDeviceID: string,
   otherDeviceID: string,
 ): boolean {
   const compareResult = currenDeviceID.localeCompare(otherDeviceID);
   if (compareResult === 0) {
     throw new Error('Comparing the same deviceIDs');
   }
   return compareResult === 1;
 }
 
 export {
   retrieveAccountKeysSet,
   getAccountPrekeysSet,
   shouldForgetPrekey,
   shouldRotatePrekey,
   getAccountOneTimeKeys,
   retrieveIdentityKeysAndPrekeys,
   hasHigherDeviceID,
   olmSessionErrors,
 };