diff --git a/lib/tunnelbroker/tunnelbroker-context.js b/lib/tunnelbroker/tunnelbroker-context.js
index 63b881321..4767def2e 100644
--- a/lib/tunnelbroker/tunnelbroker-context.js
+++ b/lib/tunnelbroker/tunnelbroker-context.js
@@ -1,231 +1,231 @@
 // @flow
 
 import invariant from 'invariant';
 import * as React from 'react';
 import uuid from 'uuid';
 
 import { tunnnelbrokerURL } from '../facts/tunnelbroker.js';
 import { tunnelbrokerHeartbeatTimeout } from '../shared/timeouts.js';
 import type { Heartbeat } from '../types/tunnelbroker/heartbeat-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 { ConnectionInitializationMessage } from '../types/tunnelbroker/session-types.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,
 };
 
 const TunnelbrokerContext: React.Context<?TunnelbrokerContextType> =
   React.createContext<?TunnelbrokerContextType>();
 
 type Props = {
   +children: React.Node,
   +initMessage: ?ConnectionInitializationMessage,
 };
 
 function TunnelbrokerProvider(props: Props): React.Node {
   const { children, initMessage } = props;
   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();
+  const heartbeatTimeoutID = React.useRef<?TimeoutID>();
 
   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]);
 
   React.useEffect(() => {
     if (connected || !initMessage) {
       return;
     }
 
     const tunnelbrokerSocket = new WebSocket(tunnnelbrokerURL);
 
     tunnelbrokerSocket.onopen = () => {
       tunnelbrokerSocket.send(JSON.stringify(initMessage));
     };
 
     tunnelbrokerSocket.onclose = () => {
       setConnected(false);
       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');
         } 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));
       } 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;
   }, [connected, initMessage, resetHeartbeatTimeout, stopHeartbeatTimeout]);
 
   const sendMessage: (message: ClientMessageToDevice) => Promise<void> =
     React.useCallback(
       (message: ClientMessageToDevice) => {
         if (!connected || !socket.current) {
           throw new Error('Tunnelbroker not connected');
         }
         const clientMessageID = uuid.v4();
         const messageToDevice: MessageToDeviceRequest = {
           type: tunnelbrokerMessageTypes.MESSAGE_TO_DEVICE_REQUEST,
           clientMessageID,
           deviceID: message.deviceID,
           payload: message.payload,
         };
 
         return new Promise((resolve, reject) => {
           promises.current[clientMessageID] = {
             resolve,
             reject,
           };
           socket.current?.send(JSON.stringify(messageToDevice));
         });
       },
       [connected],
     );
 
   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,
       addListener,
       removeListener,
     }),
     [addListener, connected, removeListener, sendMessage],
   );
 
   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/types/tunnelbroker/connection-initialization-response-types.js b/lib/types/tunnelbroker/connection-initialization-response-types.js
index 078df8259..17de9e91f 100644
--- a/lib/types/tunnelbroker/connection-initialization-response-types.js
+++ b/lib/types/tunnelbroker/connection-initialization-response-types.js
@@ -1,26 +1,31 @@
 // @flow
 
 import type { TInterface } from 'tcomb';
 import t from 'tcomb';
 
 import { tShape, tString } from '../../utils/validation-utils.js';
 
+type ConnectionInitializationSuccessStatus = { +type: 'Success' };
+type ConnectionInitializationErrorStatus = { +type: 'Error', +data: string };
 export type ConnectionInitializationStatus =
-  | { +type: 'Success' }
-  | { +type: 'Error', +data: string };
+  | ConnectionInitializationSuccessStatus
+  | ConnectionInitializationErrorStatus;
 
 const connectionInitializationStatusValidator = t.union([
-  tShape({ type: tString('Success') }),
-  tShape({ type: tString('Error'), data: t.String }),
+  tShape<ConnectionInitializationSuccessStatus>({ type: tString('Success') }),
+  tShape<ConnectionInitializationErrorStatus>({
+    type: tString('Error'),
+    data: t.String,
+  }),
 ]);
 
 export type ConnectionInitializationResponse = {
   +type: 'ConnectionInitializationResponse',
   +status: ConnectionInitializationStatus,
 };
 
 export const connectionInitializationResponseValidator: TInterface<ConnectionInitializationResponse> =
   tShape<ConnectionInitializationResponse>({
     type: tString('ConnectionInitializationResponse'),
     status: connectionInitializationStatusValidator,
   });
diff --git a/lib/types/tunnelbroker/message-to-device-request-status-types.js b/lib/types/tunnelbroker/message-to-device-request-status-types.js
index 86204c482..53163a194 100644
--- a/lib/types/tunnelbroker/message-to-device-request-status-types.js
+++ b/lib/types/tunnelbroker/message-to-device-request-status-types.js
@@ -1,40 +1,56 @@
 // @flow
 
 import type { TInterface } from 'tcomb';
 import t from 'tcomb';
 
 import { tShape, tString } from '../../utils/validation-utils.js';
 
 export type Failure = {
   +id: string,
   +error: string,
 };
 
 const failureValidator: TInterface<Failure> = tShape<Failure>({
   id: t.String,
   error: t.String,
 });
 
+type MessageSentSuccessStatus = { +type: 'Success', +data: string };
+type MessageSentErrorStatus = { +type: 'Error', +data: Failure };
+type MessageSentInvalidRequestStatus = { +type: 'InvalidRequest' };
+type MessageSentSerializationErrorStatus = {
+  +type: 'SerializationError',
+  +data: string,
+};
 export type MessageSentStatus =
-  | { +type: 'Success', +data: string }
-  | { +type: 'Error', +data: Failure }
-  | { +type: 'InvalidRequest' }
-  | { +type: 'SerializationError', +data: string };
+  | MessageSentSuccessStatus
+  | MessageSentErrorStatus
+  | MessageSentInvalidRequestStatus
+  | MessageSentSerializationErrorStatus;
 
 const messageSentStatusValidator = t.union([
-  tShape({ type: tString('Success'), data: t.String }),
-  tShape({ type: tString('Error'), data: failureValidator }),
-  tShape({ type: tString('InvalidRequest') }),
-  tShape({ type: tString('SerializationError'), data: t.String }),
+  tShape<MessageSentSuccessStatus>({
+    type: tString('Success'),
+    data: t.String,
+  }),
+  tShape<MessageSentErrorStatus>({
+    type: tString('Error'),
+    data: failureValidator,
+  }),
+  tShape<MessageSentInvalidRequestStatus>({ type: tString('InvalidRequest') }),
+  tShape<MessageSentSerializationErrorStatus>({
+    type: tString('SerializationError'),
+    data: t.String,
+  }),
 ]);
 
 export type MessageToDeviceRequestStatus = {
   +type: 'MessageToDeviceRequestStatus',
   +clientMessageIDs: $ReadOnlyArray<MessageSentStatus>,
 };
 
 export const messageToDeviceRequestStatusValidator: TInterface<MessageToDeviceRequestStatus> =
   tShape<MessageToDeviceRequestStatus>({
     type: tString('MessageToDeviceRequestStatus'),
     clientMessageIDs: t.list(messageSentStatusValidator),
   });