diff --git a/lib/reducers/thread-reducer.js b/lib/reducers/thread-reducer.js
--- a/lib/reducers/thread-reducer.js
+++ b/lib/reducers/thread-reducer.js
@@ -58,11 +58,7 @@
     +updatesResult: { +newUpdates: $ReadOnlyArray<ClientUpdateInfo>, ... },
     ...
   },
-): {
-  +threadStoreOperations: $ReadOnlyArray<ThreadStoreOperation>,
-  +threadInfos: { +[id: string]: RawThreadInfo },
-} {
-  const updatedThreadInfos = { ...threadInfos };
+): $ReadOnlyArray<ThreadStoreOperation> {
   let someThreadUpdated = false;
   const threadOperations: ThreadStoreOperation[] = [];
   for (const update of payload.updatesResult.newUpdates) {
@@ -72,7 +68,6 @@
       !_isEqual(threadInfos[update.threadInfo.id])(update.threadInfo)
     ) {
       someThreadUpdated = true;
-      updatedThreadInfos[update.threadInfo.id] = update.threadInfo;
       threadOperations.push({
         type: 'replace',
         payload: {
@@ -93,7 +88,6 @@
           unread: update.unread,
         },
       };
-      updatedThreadInfos[update.threadID] = updatedThread;
       threadOperations.push({
         type: 'replace',
         payload: {
@@ -106,7 +100,6 @@
       threadInfos[update.threadID]
     ) {
       someThreadUpdated = true;
-      delete updatedThreadInfos[update.threadID];
       threadOperations.push({
         type: 'remove',
         payload: {
@@ -125,7 +118,6 @@
             ...threadInfo,
             members: newMembers,
           };
-          updatedThreadInfos[threadID] = updatedThread;
           threadOperations.push({
             type: 'replace',
             payload: {
@@ -138,12 +130,9 @@
     }
   }
   if (!someThreadUpdated) {
-    return { threadStoreOperations: [], threadInfos };
+    return [];
   }
-  return {
-    threadStoreOperations: threadOperations,
-    threadInfos: updatedThreadInfos,
-  };
+  return threadOperations;
 }
 
 function findInconsistencies(
@@ -244,7 +233,7 @@
         threadStoreOperations: [],
       };
     }
-    const { threadStoreOperations } = reduceThreadUpdates(
+    const threadStoreOperations = reduceThreadUpdates(
       state.threadInfos,
       action.payload,
     );