diff --git a/keyserver/src/fetchers/relationship-fetchers.js b/keyserver/src/fetchers/relationship-fetchers.js
--- a/keyserver/src/fetchers/relationship-fetchers.js
+++ b/keyserver/src/fetchers/relationship-fetchers.js
@@ -48,7 +48,7 @@
     result,
   );
 
-  const errors: RelationshipErrors = {};
+  let errors: RelationshipErrors = {};
   const userRelationshipOperations: UserRelationshipOperations = {};
   for (const userID in relationshipsByUserId) {
     const relationships = relationshipsByUserId[userID];
@@ -83,10 +83,10 @@
         operations.push('delete_directed');
       }
       const user_blocked = errors.user_blocked || [];
-      errors.user_blocked = [...user_blocked, userID];
+      errors = { ...errors, user_blocked: [...user_blocked, userID] };
     } else if (friendshipExists) {
       const already_friends = errors.already_friends || [];
-      errors.already_friends = [...already_friends, userID];
+      errors = { ...errors, already_friends: [...already_friends, userID] };
     } else if (targetRequestedViewerFriendship) {
       operations.push('friend', 'delete_directed');
     } else if (!viewerRequestedTargetFriendship) {
diff --git a/keyserver/src/updaters/relationship-updaters.js b/keyserver/src/updaters/relationship-updaters.js
--- a/keyserver/src/updaters/relationship-updaters.js
+++ b/keyserver/src/updaters/relationship-updaters.js
@@ -46,7 +46,7 @@
   for (const userID of uniqueUserIDs) {
     if (userID === viewer.userID || !users[userID].username) {
       const acc = errors.invalid_user || [];
-      errors.invalid_user = [...acc, userID];
+      errors = { ...errors, invalid_user: [...acc, userID] };
     } else {
       userIDs.push(userID);
     }
diff --git a/lib/shared/dm-ops/create-thread-spec.js b/lib/shared/dm-ops/create-thread-spec.js
--- a/lib/shared/dm-ops/create-thread-spec.js
+++ b/lib/shared/dm-ops/create-thread-spec.js
@@ -103,11 +103,10 @@
   };
 }
 
-type MutableThickRawThreadInfo = { ...ThickRawThreadInfo };
 function createThickRawThreadInfo(
   input: CreateThickRawThreadInfoInput,
   utilities: ProcessDMOperationUtilities,
-): MutableThickRawThreadInfo {
+): ThickRawThreadInfo {
   const {
     threadID,
     threadType,
@@ -159,7 +158,7 @@
     parentThreadInfo,
   );
 
-  const newThread: MutableThickRawThreadInfo = {
+  let newThread: ThickRawThreadInfo = {
     thick: true,
     minimallyEncoded: true,
     id: threadID,
@@ -197,10 +196,10 @@
     timestamps,
   };
   if (sourceMessageID) {
-    newThread.sourceMessageID = sourceMessageID;
+    newThread = { ...newThread, sourceMessageID };
   }
   if (pinnedCount) {
-    newThread.pinnedCount = pinnedCount;
+    newThread = { ...newThread, pinnedCount };
   }
   return newThread;
 }