diff --git a/lib/shared/dm-ops/join-thread-spec.js b/lib/shared/dm-ops/join-thread-spec.js
--- a/lib/shared/dm-ops/join-thread-spec.js
+++ b/lib/shared/dm-ops/join-thread-spec.js
@@ -32,7 +32,7 @@
     viewerID: string,
     utilities: ProcessDMOperationUtilities,
   ) => {
-    const { editorID, time, messageID, existingThreadDetails } = dmOperation;
+    const { joinerID, time, messageID, existingThreadDetails } = dmOperation;
 
     const currentThreadInfo =
       utilities.threadInfos[existingThreadDetails.threadID];
@@ -41,11 +41,11 @@
       type: messageTypes.JOIN_THREAD,
       id: messageID,
       threadID: existingThreadDetails.threadID,
-      creatorID: editorID,
+      creatorID: joinerID,
       time,
     };
 
-    if (userIsMember(currentThreadInfo, editorID)) {
+    if (userIsMember(currentThreadInfo, joinerID)) {
       return {
         rawMessageInfos: [joinThreadMessage],
         updateInfos: [
@@ -62,11 +62,11 @@
 
     const updateInfos: Array<ClientUpdateInfo> = [];
     const rawMessageInfos: Array<RawMessageInfo> = [];
-    if (viewerID === editorID) {
+    if (viewerID === joinerID) {
       const newThreadInfo = createThickRawThreadInfo(
         {
           ...existingThreadDetails,
-          allMemberIDs: [...existingThreadDetails.allMemberIDs, editorID],
+          allMemberIDs: [...existingThreadDetails.allMemberIDs, joinerID],
         },
         viewerID,
       );
@@ -109,10 +109,10 @@
       );
 
       const member = minimallyEncodeMemberInfo<ThickMemberInfo>({
-        id: editorID,
+        id: joinerID,
         role: defaultRoleID,
         permissions: membershipPermissions,
-        isSender: editorID === viewerID,
+        isSender: joinerID === viewerID,
         subscription: joinThreadSubscription,
       });
       const updatedThreadInfo = {
diff --git a/lib/types/dm-ops.js b/lib/types/dm-ops.js
--- a/lib/types/dm-ops.js
+++ b/lib/types/dm-ops.js
@@ -193,7 +193,7 @@
 
 export type DMJoinThreadOperation = {
   +type: 'join_thread',
-  +editorID: string,
+  +joinerID: string,
   +time: number,
   +messageID: string,
   +existingThreadDetails: CreateThickRawThreadInfoInput,
@@ -201,7 +201,7 @@
 export const dmJoinThreadOperationValidator: TInterface<DMJoinThreadOperation> =
   tShape<DMJoinThreadOperation>({
     type: tString(dmOperationTypes.JOIN_THREAD),
-    editorID: tUserID,
+    joinerID: tUserID,
     time: t.Number,
     messageID: t.String,
     existingThreadDetails: createThickRawThreadInfoInputValidator,