diff --git a/src/event-source.ts b/src/event-source.ts
index ef384da..53029f1 100644
--- a/src/event-source.ts
+++ b/src/event-source.ts
@@ -3,14 +3,17 @@ import {Status, PartialStatus} from './state/status';
 import {empty} from 'rxjs/observable/empty';
 import {of} from 'rxjs/observable/of';
 import {IncomingMessage} from './state/message';
-import {Channel} from './state/channel';
-import {InstantMessage} from './state/ims';
+import {Channel, isChannel} from './state/channel';
+import {InstantMessage, isInstantMessage} from './state/ims';
 import {findOne} from './util/map'
 type O<T> = Observable<T>;
+type BothPS = PartialStatus<IncomingMessage<Channel> | IncomingMessage<InstantMessage>>;
+type ChanPS = PartialStatus<IncomingMessage<Channel>>;
+type IMPS = PartialStatus<IncomingMessage<InstantMessage>>;
 
 export class EventSource {
 
-    private _message$: O<PartialStatus<IncomingMessage<Channel> | IncomingMessage<InstantMessage>>>;
+    private _message$: O<BothPS>;
 
     constructor(_status$: Observable<Status>) {
         const [, message$] = _status$.partition(status => typeof status.event === 'string');
@@ -19,7 +22,7 @@ export class EventSource {
     }
 
     selectByChannelName(name: string): Observable<IncomingMessage<Channel>> {
-        return this._message$.mergeMap(({event, channels}) => {
+        return this._message$.filter<BothPS, ChanPS>((ps: BothPS): ps is ChanPS => isChannel(ps.event.channel)).mergeMap(({event, channels}) => {
             const channel = findOne(channel => name === channel.name, channels);
             if (channel && !event.user.is_bot) {
                 return of(event);
@@ -30,7 +33,7 @@ export class EventSource {
     }
 
     selectByUserName(name: string): Observable<IncomingMessage<InstantMessage>> {
-        return this._message$.mergeMap(({users, event, ims}) => {
+        return this._message$.filter<BothPS, IMPS>((ps: BothPS): ps is IMPS => isInstantMessage(ps.event.channel)).mergeMap(({users, event, ims}) => {
             const user = findOne(user => name === user.name, users);
             if (!user) {
                 return empty();
diff --git a/src/state/channel.ts b/src/state/channel.ts
index 2fc237d..9c3223d 100644
--- a/src/state/channel.ts
+++ b/src/state/channel.ts
@@ -1,4 +1,4 @@
-import {where, is, pick, assoc} from 'ramda';
+import {pick, assoc} from 'ramda';
 
 export type Channel = {
     id: string;
@@ -9,14 +9,16 @@ export type Channel = {
     creator: string;
 }
 
-export const isChannel = where({
-    id: is(String),
-    name: is(String),
-    is_member: is(Boolean),
-    is_archived: is(Boolean),
-    created: is(Number),
-    creator: is(String)
-});
+export function isChannel(x: any): x is Channel {
+    return typeof x === 'object' &&
+        x !== null &&
+        typeof x.id === 'string' &&
+        typeof x.name === 'string' &&
+        typeof x.is_member === 'boolean' &&
+        typeof x.is_archived === 'boolean' &&
+        typeof x.created === 'number' &&
+        typeof x.creator === 'string';
+};
 
 const channelKeyList: Array<keyof Channel> = [
     'id',
diff --git a/src/state/ims.ts b/src/state/ims.ts
index 2b9f848..0df283b 100644
--- a/src/state/ims.ts
+++ b/src/state/ims.ts
@@ -1,4 +1,4 @@
-import {where, is, pick} from 'ramda';
+import {pick} from 'ramda';
 
 export type InstantMessage = {
     id: string;
@@ -7,12 +7,14 @@ export type InstantMessage = {
     created: number;
 }
 
-export const isInstantMessage = where({
-    id: is(String),
-    user: is(String),
-    is_open: is(Boolean),
-    created: is(Number)
-});
+export function isInstantMessage(x: any): x is InstantMessage {
+    return typeof x === 'object' &&
+        x !== null &&
+        typeof x.id === 'string' &&
+        typeof x.user === 'string' &&
+        typeof x.is_open === 'boolean' &&
+        typeof x.created === 'number';
+};
 
 const imKeyList: Array<keyof InstantMessage> = [
     'id',
diff --git a/src/state/status.ts b/src/state/status.ts
index b1f8e35..5998f43 100644
--- a/src/state/status.ts
+++ b/src/state/status.ts
@@ -53,7 +53,7 @@ export function updateChannel(key: string, project: (x: Channel) => Channel): Ac
 }
 
 export function deleteChannel(key: string): Action {
-    return curryDel(key);
+    return over(lensProp('channels'), curryDel(key));
 }
 
 export function updateUser(key: string, project: (x: User) => User): Action {