diff --git a/lib/reducers/message-reducer.js b/lib/reducers/message-reducer.js
--- a/lib/reducers/message-reducer.js
+++ b/lib/reducers/message-reducer.js
@@ -1315,6 +1315,7 @@
     for (const id in actionPayloadMessages) {
       const message = actionPayloadMessages[id];
       const { threadID } = message;
+      const existingThread = threads[threadID] ?? newThread();
       if (
         (message.type === messageTypes.IMAGES ||
           message.type === messageTypes.MULTIMEDIA) &&
@@ -1324,8 +1325,8 @@
         threads = {
           ...threads,
           [threadID]: {
-            ...threads[threadID],
-            messageIDs: threads[threadID].messageIDs.filter(
+            ...existingThread,
+            messageIDs: existingThread.messageIDs.filter(
               curMessageID => curMessageID !== id,
             ),
           },
@@ -1337,11 +1338,13 @@
         threads = {
           ...threads,
           [threadID]: {
-            ...threads[threadID],
-            messageIDs: [...threads[threadID].messageIDs, id],
+            ...existingThread,
+            messageIDs: [...existingThread.messageIDs, id],
           },
         };
         threadsNeedMsgIDsResorting.add(threadID);
+      } else if (!threads[threadID]) {
+        threads = { ...threads, [threadID]: existingThread };
       }
     }