diff --git a/lib/reducers/thread-activity-reducer.js b/lib/reducers/thread-activity-reducer.js
index 459b2a320..255c87313 100644
--- a/lib/reducers/thread-activity-reducer.js
+++ b/lib/reducers/thread-activity-reducer.js
@@ -1,37 +1,61 @@
 // @flow
 
+import {
+  deleteThreadActionTypes,
+  leaveThreadActionTypes,
+} from '../actions/thread-actions.js';
 import {
   logOutActionTypes,
   deleteAccountActionTypes,
 } from '../actions/user-actions.js';
 import type { BaseAction } from '../types/redux-types.js';
 import type { ThreadActivityStore } from '../types/thread-activity-types.js';
 import { updateThreadLastNavigatedActionType } from '../types/thread-activity-types.js';
+import { updateTypes } from '../types/update-types-enum.js';
+import type { ClientUpdateInfo } from '../types/update-types.js';
 import { setNewSessionActionType } from '../utils/action-utils.js';
 
 function reduceThreadActivity(
   state: ThreadActivityStore,
   action: BaseAction,
 ): ThreadActivityStore {
   if (action.type === updateThreadLastNavigatedActionType) {
     const { threadID, time } = action.payload;
     const updatedThreadActivityStore = {
       ...state,
       [threadID]: {
         ...state[threadID],
         lastNavigatedTo: time,
       },
     };
     return updatedThreadActivityStore;
+  } else if (
+    action.type === leaveThreadActionTypes.success ||
+    action.type === deleteThreadActionTypes.success
+  ) {
+    const { newUpdates } = action.payload.updatesResult;
+    if (newUpdates.length === 0) {
+      return state;
+    }
+
+    let updatedState = { ...state };
+    for (const update: ClientUpdateInfo of newUpdates) {
+      if (update.type === updateTypes.DELETE_THREAD) {
+        const { [update.threadID]: _, ...stateSansRemovedThread } =
+          updatedState;
+        updatedState = stateSansRemovedThread;
+      }
+    }
+    return updatedState;
   } else if (
     action.type === logOutActionTypes.success ||
     action.type === deleteAccountActionTypes.success ||
     (action.type === setNewSessionActionType &&
       action.payload.sessionChange.cookieInvalidated)
   ) {
     return {};
   }
   return state;
 }
 
 export { reduceThreadActivity };