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
@@ -97,7 +97,7 @@
 const _mapValuesWithKeys = _mapValues.convert({ cap: false });
 
 // Input must already be ordered!
-function threadsToMessageIDsFromMessageInfos(
+function mapThreadsToMessageIDsFromOrderedMessageInfos(
   orderedMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 ): { [threadID: string]: string[] } {
   const threads: { [threadID: string]: string[] } = {};
@@ -144,7 +144,7 @@
     payload: { id: messageID(messageInfo), messageInfo },
   }));
 
-  const threadsToMessageIDs = threadsToMessageIDsFromMessageInfos(
+  const threadsToMessageIDs = mapThreadsToMessageIDsFromOrderedMessageInfos(
     orderedMessageInfos,
   );
   const lastPruned = Date.now();
@@ -406,7 +406,7 @@
   )(unshimmedNewMessagesOfWatchedThreads);
 
   const newMessageOps: MessageStoreOperation[] = [];
-  const threadsToMessageIDs = threadsToMessageIDsFromMessageInfos(
+  const threadsToMessageIDs = mapThreadsToMessageIDsFromOrderedMessageInfos(
     orderedNewMessageInfos,
   );
   const oldMessageInfosToCombine = [];