diff --git a/lib/reducers/dm-operations-queue-reducer.js b/lib/reducers/dm-operations-queue-reducer.js
--- a/lib/reducers/dm-operations-queue-reducer.js
+++ b/lib/reducers/dm-operations-queue-reducer.js
@@ -10,6 +10,7 @@
   clearQueuedThreadDMOpsActionType,
   type OperationsQueue,
   pruneDMOpsQueueActionType,
+  queuedDMOperationConditionType,
   type QueuedDMOperations,
   queueDMOpsActionType,
   reportUnshimmingOperationCompletedActionType,
@@ -27,7 +28,7 @@
   if (action.type === queueDMOpsActionType) {
     const { condition, operation, timestamp } = action.payload;
 
-    if (condition.type === 'thread') {
+    if (condition.type === queuedDMOperationConditionType.THREAD) {
       return {
         store: {
           ...store,
@@ -43,7 +44,7 @@
       };
     }
 
-    if (condition.type === 'entry') {
+    if (condition.type === queuedDMOperationConditionType.ENTRY) {
       return {
         store: {
           ...store,
@@ -59,7 +60,7 @@
       };
     }
 
-    if (condition.type === 'message') {
+    if (condition.type === queuedDMOperationConditionType.MESSAGE) {
       return {
         store: {
           ...store,
diff --git a/lib/shared/dm-ops/process-dm-ops.js b/lib/shared/dm-ops/process-dm-ops.js
--- a/lib/shared/dm-ops/process-dm-ops.js
+++ b/lib/shared/dm-ops/process-dm-ops.js
@@ -33,6 +33,7 @@
   dmOperationValidator,
   type ProcessDMOpsPayload,
   saveUnsupportedOperationActionType,
+  queuedDMOperationConditionType,
 } from '../../types/dm-ops.js';
 import type { RawMessageInfo } from '../../types/message-types.js';
 import type { DispatchMetadata } from '../../types/redux-types.js';
@@ -188,22 +189,22 @@
         let condition;
         if (processingCheckResult.reason.type === 'missing_thread') {
           condition = {
-            type: 'thread',
+            type: queuedDMOperationConditionType.THREAD,
             threadID: processingCheckResult.reason.threadID,
           };
         } else if (processingCheckResult.reason.type === 'missing_entry') {
           condition = {
-            type: 'entry',
+            type: queuedDMOperationConditionType.ENTRY,
             entryID: processingCheckResult.reason.entryID,
           };
         } else if (processingCheckResult.reason.type === 'missing_message') {
           condition = {
-            type: 'message',
+            type: queuedDMOperationConditionType.MESSAGE,
             messageID: processingCheckResult.reason.messageID,
           };
         } else if (processingCheckResult.reason.type === 'missing_membership') {
           condition = {
-            type: 'membership',
+            type: queuedDMOperationConditionType.MEMBERSHIP,
             threadID: processingCheckResult.reason.threadID,
             userID: processingCheckResult.reason.userID,
           };
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
@@ -1,5 +1,6 @@
 // @flow
 
+import invariant from 'invariant';
 import t, { type TInterface, type TUnion } from 'tcomb';
 
 import { clientAvatarValidator, type ClientAvatar } from './avatar-types.js';
@@ -555,28 +556,53 @@
   +messagesNotifyTypes: { +[messageID: string]: MessageNotifyType },
 };
 
+export const queuedDMOperationConditionType = Object.freeze({
+  THREAD: 'thread',
+  ENTRY: 'entry',
+  MESSAGE: 'message',
+  MEMBERSHIP: 'membership',
+});
+export type QueuedDMOperationCondition = $Values<
+  typeof queuedDMOperationConditionType,
+>;
+
+export function assertQueuedDMOperationCondition(
+  queuedDMOperationCondition: string,
+): QueuedDMOperationCondition {
+  invariant(
+    queuedDMOperationCondition === 'thread' ||
+      queuedDMOperationCondition === 'entry' ||
+      queuedDMOperationCondition === 'message' ||
+      queuedDMOperationCondition === 'membership',
+    'string is not QueuedDMOperationCondition enum',
+  );
+  return queuedDMOperationCondition;
+}
+
+export type QueueDMOpsCondition =
+  | {
+      +type: 'thread',
+      +threadID: string,
+    }
+  | {
+      +type: 'entry',
+      +entryID: string,
+    }
+  | {
+      +type: 'message',
+      +messageID: string,
+    }
+  | {
+      +type: 'membership',
+      +threadID: string,
+      +userID: string,
+    };
+
 export const queueDMOpsActionType = 'QUEUE_DM_OPS';
 export type QueueDMOpsPayload = {
   +operation: DMOperation,
   +timestamp: number,
-  +condition:
-    | {
-        +type: 'thread',
-        +threadID: string,
-      }
-    | {
-        +type: 'entry',
-        +entryID: string,
-      }
-    | {
-        +type: 'message',
-        +messageID: string,
-      }
-    | {
-        +type: 'membership',
-        +threadID: string,
-        +userID: string,
-      },
+  +condition: QueueDMOpsCondition,
 };
 
 export const pruneDMOpsQueueActionType = 'PRUNE_DM_OPS_QUEUE';