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
@@ -1301,9 +1301,9 @@
     const now = Date.now();
     const messageIDsToPrune = [];
 
-    const newThreads = { ...messageStore.threads };
+    const updatedThreads = {};
     for (const threadID of action.payload.threadIDs) {
-      let thread = newThreads[threadID];
+      let thread = messageStore.threads[threadID];
       if (!thread) {
         continue;
       }
@@ -1322,7 +1322,7 @@
         messageIDsToPrune.push(id);
       }
 
-      newThreads[threadID] = thread;
+      updatedThreads[threadID] = thread;
     }
 
     const messageStoreOperations = [
@@ -1330,20 +1330,38 @@
         type: 'remove',
         payload: { ids: messageIDsToPrune },
       },
+      {
+        type: 'replace_threads',
+        payload: {
+          threads: updatedThreads,
+        },
+      },
     ];
+
     const processedMessageStore = processMessageStoreOperations(
       messageStore,
       messageStoreOperations,
     );
 
+    const newMessageStore = {
+      messages: processedMessageStore.messages,
+      threads: {
+        ...messageStore.threads,
+        ...updatedThreads,
+      },
+      local: _omit(messageIDsToPrune)(messageStore.local),
+      currentAsOf: messageStore.currentAsOf,
+    };
+
+    assertMessageStoreThreadsAreEqual(
+      processedMessageStore,
+      newMessageStore,
+      action.type,
+    );
+
     return {
       messageStoreOperations,
-      messageStore: {
-        messages: processedMessageStore.messages,
-        threads: newThreads,
-        local: _omit(messageIDsToPrune)(messageStore.local),
-        currentAsOf: messageStore.currentAsOf,
-      },
+      messageStore: newMessageStore,
     };
   } else if (action.type === updateMultimediaMessageMediaActionType) {
     const { messageID: id, currentMediaID, mediaUpdate } = action.payload;