diff --git a/app/actions/customEmojis.js b/app/actions/customEmojis.js
deleted file mode 100644
index 740a936ac..000000000
--- a/app/actions/customEmojis.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import * as types from './actionsTypes';
-
-export function setCustomEmojis(emojis) {
-	return {
-		type: types.SET_CUSTOM_EMOJIS,
-		emojis
-	};
-}
diff --git a/app/actions/customEmojis.ts b/app/actions/customEmojis.ts
new file mode 100644
index 000000000..261fbd241
--- /dev/null
+++ b/app/actions/customEmojis.ts
@@ -0,0 +1,17 @@
+import { Action } from 'redux';
+
+import { ICustomEmojis } from '../reducers/customEmojis';
+import { SET_CUSTOM_EMOJIS } from './actionsTypes';
+
+export interface ISetCustomEmojis extends Action {
+	emojis: ICustomEmojis;
+}
+
+export type TActionCustomEmojis = ISetCustomEmojis;
+
+export function setCustomEmojis(emojis: ICustomEmojis): ISetCustomEmojis {
+	return {
+		type: SET_CUSTOM_EMOJIS,
+		emojis
+	};
+}
diff --git a/app/definitions/redux/index.ts b/app/definitions/redux/index.ts
index f3e3c792b..54eb6e4c4 100644
--- a/app/definitions/redux/index.ts
+++ b/app/definitions/redux/index.ts
@@ -1,4 +1,5 @@
 import { TActionActiveUsers } from '../../actions/activeUsers';
+import { TActionCustomEmojis } from '../../actions/customEmojis';
 import { TActionEncryption } from '../../actions/encryption';
 import { TActionInviteLinks } from '../../actions/inviteLinks';
 import { IActionRoles } from '../../actions/roles';
@@ -36,4 +37,10 @@ export interface IApplicationState {
 	roles: IRoles;
 }
 
-export type TApplicationActions = TActionActiveUsers & TActionSelectedUsers & TActionEncryption& TActionInviteLinks & IActionRoles & IActionSettings;
+export type TApplicationActions = TActionActiveUsers &
+	TActionSelectedUsers &
+	TActionCustomEmojis &
+	TActionInviteLinks &
+	IActionRoles &
+	IActionSettings &
+	TActionEncryption;
diff --git a/app/reducers/customEmojis.js b/app/reducers/customEmojis.js
deleted file mode 100644
index fbdaeab80..000000000
--- a/app/reducers/customEmojis.js
+++ /dev/null
@@ -1,14 +0,0 @@
-import { SET_CUSTOM_EMOJIS } from '../actions/actionsTypes';
-
-const initialState = {
-	customEmojis: {}
-};
-
-export default function customEmojis(state = initialState, action) {
-	switch (action.type) {
-		case SET_CUSTOM_EMOJIS:
-			return action.emojis;
-		default:
-			return state;
-	}
-}
diff --git a/app/reducers/customEmojis.test.ts b/app/reducers/customEmojis.test.ts
new file mode 100644
index 000000000..3f507f04c
--- /dev/null
+++ b/app/reducers/customEmojis.test.ts
@@ -0,0 +1,16 @@
+import { setCustomEmojis } from '../actions/customEmojis';
+import { ICustomEmojis, initialState } from './customEmojis';
+import { mockedStore } from './mockedStore';
+
+describe('test reducer', () => {
+	it('should return initial state', () => {
+		const state = mockedStore.getState().customEmojis;
+		expect(state).toEqual(initialState);
+	});
+	it('should return modified store after action', () => {
+		const emojis: ICustomEmojis = { dog: { name: 'dog', extension: 'jpg' }, cat: { name: 'cat', extension: 'jpg' } };
+		mockedStore.dispatch(setCustomEmojis(emojis));
+		const state = mockedStore.getState().customEmojis;
+		expect(state).toEqual(emojis);
+	});
+});
diff --git a/app/reducers/customEmojis.ts b/app/reducers/customEmojis.ts
new file mode 100644
index 000000000..859d634d4
--- /dev/null
+++ b/app/reducers/customEmojis.ts
@@ -0,0 +1,23 @@
+import { SET_CUSTOM_EMOJIS } from '../actions/actionsTypes';
+import { TApplicationActions } from '../definitions';
+
+// There are at least three interfaces for emoji, but none of them includes only this data.
+interface IEmoji {
+	name: string;
+	extension: string;
+}
+
+export interface ICustomEmojis {
+	[key: string]: IEmoji;
+}
+
+export const initialState: ICustomEmojis = {};
+
+export default function customEmojis(state = initialState, action: TApplicationActions): ICustomEmojis {
+	switch (action.type) {
+		case SET_CUSTOM_EMOJIS:
+			return action.emojis;
+		default:
+			return state;
+	}
+}