diff --git a/app/actions/activeUsers.js b/app/actions/activeUsers.js
deleted file mode 100644
index fc359602c..000000000
--- a/app/actions/activeUsers.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { SET_ACTIVE_USERS } from './actionsTypes';
-
-export function setActiveUsers(activeUsers) {
-	return {
-		type: SET_ACTIVE_USERS,
-		activeUsers
-	};
-}
diff --git a/app/actions/activeUsers.ts b/app/actions/activeUsers.ts
new file mode 100644
index 000000000..3e6271ee9
--- /dev/null
+++ b/app/actions/activeUsers.ts
@@ -0,0 +1,14 @@
+import { Action } from 'redux';
+
+import { ActiveUsers } from '../reducers/activeUsers';
+import { SET_ACTIVE_USERS } from './actionsTypes';
+
+export interface SetActiveUsers extends Action {
+	type: typeof SET_ACTIVE_USERS;
+	activeUsers: ActiveUsers;
+}
+
+export const setActiveUsers = (activeUsers: ActiveUsers): SetActiveUsers => ({
+	type: SET_ACTIVE_USERS,
+	activeUsers
+});
diff --git a/app/reducers/activeUsers.js b/app/reducers/activeUsers.js
deleted file mode 100644
index 8f6c5b38a..000000000
--- a/app/reducers/activeUsers.js
+++ /dev/null
@@ -1,15 +0,0 @@
-import { SET_ACTIVE_USERS } from '../actions/actionsTypes';
-
-const initialState = {};
-
-export default function activeUsers(state = initialState, action) {
-	switch (action.type) {
-		case SET_ACTIVE_USERS:
-			return {
-				...state,
-				...action.activeUsers
-			};
-		default:
-			return state;
-	}
-}
diff --git a/app/reducers/activeUsers.ts b/app/reducers/activeUsers.ts
new file mode 100644
index 000000000..306c24e7e
--- /dev/null
+++ b/app/reducers/activeUsers.ts
@@ -0,0 +1,27 @@
+import { SetActiveUsers } from '../actions/activeUsers';
+import { SET_ACTIVE_USERS } from '../actions/actionsTypes';
+
+type UserStatus = 'online' | 'offline';
+
+interface ActiveUser {
+	readonly status: UserStatus;
+	readonly statusText?: string;
+}
+
+export interface ActiveUsers {
+	[key: string]: ActiveUser;
+}
+
+const initialState: ActiveUsers = {};
+
+export default function activeUsers(state = initialState, action: SetActiveUsers): ActiveUsers {
+	switch (action.type) {
+		case SET_ACTIVE_USERS:
+			return {
+				...state,
+				...action.activeUsers
+			};
+		default:
+			return state;
+	}
+}