diff --git a/lib/shared/dm-ops/add-members-spec.js b/lib/shared/dm-ops/add-members-spec.js
--- a/lib/shared/dm-ops/add-members-spec.js
+++ b/lib/shared/dm-ops/add-members-spec.js
@@ -8,7 +8,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMAddMembersOperation } from '../../types/dm-ops.js';
+import {
+  type DMAddMembersOperation,
+  dmAddMembersOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { RawMessageInfo } from '../../types/message-types.js';
 import type { AddMembersMessageData } from '../../types/messages/add-members.js';
@@ -166,6 +169,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmAddMembersOperationValidator,
 });
 
 export {
diff --git a/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js b/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
--- a/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
+++ b/lib/shared/dm-ops/add-viewer-to-thread-members-spec.js
@@ -7,7 +7,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMAddViewerToThreadMembersOperation } from '../../types/dm-ops.js';
+import {
+  type DMAddViewerToThreadMembersOperation,
+  dmAddViewerToThreadMembersValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { RawMessageInfo } from '../../types/message-types.js';
 import { messageTruncationStatus } from '../../types/message-types.js';
@@ -157,6 +160,7 @@
       };
     },
     supportsAutoRetry: true,
+    operationValidator: dmAddViewerToThreadMembersValidator,
   });
 
 export {
diff --git a/lib/shared/dm-ops/change-thread-read-status-spec.js b/lib/shared/dm-ops/change-thread-read-status-spec.js
--- a/lib/shared/dm-ops/change-thread-read-status-spec.js
+++ b/lib/shared/dm-ops/change-thread-read-status-spec.js
@@ -6,8 +6,11 @@
 import type {
   DMOperationSpec,
   ProcessDMOperationUtilities,
-} from './dm-op-spec';
-import type { DMChangeThreadReadStatusOperation } from '../../types/dm-ops';
+} from './dm-op-spec.js';
+import {
+  type DMChangeThreadReadStatusOperation,
+  dmChangeThreadReadStatusOperationValidator,
+} from '../../types/dm-ops.js';
 import { updateTypes } from '../../types/update-types-enum.js';
 
 const changeThreadReadStatusSpec: DMOperationSpec<DMChangeThreadReadStatusOperation> =
@@ -72,6 +75,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: true,
+    operationValidator: dmChangeThreadReadStatusOperationValidator,
   });
 
 export { changeThreadReadStatusSpec };
diff --git a/lib/shared/dm-ops/change-thread-settings-spec.js b/lib/shared/dm-ops/change-thread-settings-spec.js
--- a/lib/shared/dm-ops/change-thread-settings-spec.js
+++ b/lib/shared/dm-ops/change-thread-settings-spec.js
@@ -8,10 +8,11 @@
   ProcessDMOperationUtilities,
   ProcessingPossibilityCheckResult,
 } from './dm-op-spec.js';
-import type {
-  DMBlobOperation,
-  DMChangeThreadSettingsOperation,
-  DMThreadSettingsChanges,
+import {
+  type DMBlobOperation,
+  type DMChangeThreadSettingsOperation,
+  type DMThreadSettingsChanges,
+  dmChangeThreadSettingsOperationValidator,
 } from '../../types/dm-ops.js';
 import type { RawMessageInfo } from '../../types/message-types';
 import { messageTypes } from '../../types/message-types-enum.js';
@@ -246,6 +247,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: true,
+    operationValidator: dmChangeThreadSettingsOperationValidator,
   });
 
 export { changeThreadSettingsSpec, createChangeSettingsMessageDatasAndUpdate };
diff --git a/lib/shared/dm-ops/change-thread-subscription.js b/lib/shared/dm-ops/change-thread-subscription.js
--- a/lib/shared/dm-ops/change-thread-subscription.js
+++ b/lib/shared/dm-ops/change-thread-subscription.js
@@ -7,7 +7,10 @@
   ProcessDMOperationUtilities,
   DMOperationSpec,
 } from './dm-op-spec.js';
-import type { DMChangeThreadSubscriptionOperation } from '../../types/dm-ops.js';
+import {
+  type DMChangeThreadSubscriptionOperation,
+  dmChangeThreadSubscriptionOperationValidator,
+} from '../../types/dm-ops.js';
 import { updateTypes } from '../../types/update-types-enum.js';
 import type { ClientUpdateInfo } from '../../types/update-types.js';
 
@@ -108,6 +111,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: true,
+    operationValidator: dmChangeThreadSubscriptionOperationValidator,
   });
 
 export { changeThreadSubscriptionSpec };
diff --git a/lib/shared/dm-ops/create-entry-spec.js b/lib/shared/dm-ops/create-entry-spec.js
--- a/lib/shared/dm-ops/create-entry-spec.js
+++ b/lib/shared/dm-ops/create-entry-spec.js
@@ -6,7 +6,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMCreateEntryOperation } from '../../types/dm-ops.js';
+import {
+  type DMCreateEntryOperation,
+  dmCreateEntryOperationValidator,
+} from '../../types/dm-ops.js';
 import type { ThickRawEntryInfo } from '../../types/entry-types.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { updateTypes } from '../../types/update-types-enum.js';
@@ -103,6 +106,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmCreateEntryOperationValidator,
 });
 
 export { createEntrySpec };
diff --git a/lib/shared/dm-ops/create-sidebar-spec.js b/lib/shared/dm-ops/create-sidebar-spec.js
--- a/lib/shared/dm-ops/create-sidebar-spec.js
+++ b/lib/shared/dm-ops/create-sidebar-spec.js
@@ -7,7 +7,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMCreateSidebarOperation } from '../../types/dm-ops.js';
+import {
+  type DMCreateSidebarOperation,
+  dmCreateSidebarOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import {
   type RawMessageInfo,
@@ -251,6 +254,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: true,
+    operationValidator: dmCreateSidebarOperationValidator,
   });
 
 export { createSidebarSpec };
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
@@ -14,9 +14,10 @@
   getThickThreadRolePermissionsBlob,
   makePermissionsForChildrenBlob,
 } from '../../permissions/thread-permissions.js';
-import type {
-  CreateThickRawThreadInfoInput,
-  DMCreateThreadOperation,
+import {
+  type CreateThickRawThreadInfoInput,
+  type DMCreateThreadOperation,
+  dmCreateThreadOperationValidator,
 } from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { messageTruncationStatus } from '../../types/message-types.js';
@@ -309,6 +310,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: true,
+    operationValidator: dmCreateThreadOperationValidator,
   });
 
 export {
diff --git a/lib/shared/dm-ops/delete-entry-spec.js b/lib/shared/dm-ops/delete-entry-spec.js
--- a/lib/shared/dm-ops/delete-entry-spec.js
+++ b/lib/shared/dm-ops/delete-entry-spec.js
@@ -7,7 +7,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMDeleteEntryOperation } from '../../types/dm-ops.js';
+import {
+  type DMDeleteEntryOperation,
+  dmDeleteEntryOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { updateTypes } from '../../types/update-types-enum.js';
 import type { EntryUpdateInfo } from '../../types/update-types.js';
@@ -116,6 +119,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmDeleteEntryOperationValidator,
 });
 
 export { deleteEntrySpec };
diff --git a/lib/shared/dm-ops/dm-op-spec.js b/lib/shared/dm-ops/dm-op-spec.js
--- a/lib/shared/dm-ops/dm-op-spec.js
+++ b/lib/shared/dm-ops/dm-op-spec.js
@@ -1,5 +1,7 @@
 // @flow
 
+import type { TInterface } from 'tcomb';
+
 import type { DMOperation, DMOperationResult } from '../../types/dm-ops.js';
 import type { RawEntryInfos } from '../../types/entry-types.js';
 import type { UserIdentitiesResponse } from '../../types/identity-service-types.js';
@@ -44,4 +46,5 @@
     utilities: ProcessDMOperationUtilities,
   ) => Promise<ProcessingPossibilityCheckResult>,
   +supportsAutoRetry: boolean,
+  +operationValidator: TInterface<DMOp>,
 };
diff --git a/lib/shared/dm-ops/edit-entry-spec.js b/lib/shared/dm-ops/edit-entry-spec.js
--- a/lib/shared/dm-ops/edit-entry-spec.js
+++ b/lib/shared/dm-ops/edit-entry-spec.js
@@ -7,7 +7,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMEditEntryOperation } from '../../types/dm-ops.js';
+import {
+  type DMEditEntryOperation,
+  dmEditEntryOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { updateTypes } from '../../types/update-types-enum.js';
 import type { EntryUpdateInfo } from '../../types/update-types.js';
@@ -117,6 +120,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmEditEntryOperationValidator,
 });
 
 export { editEntrySpec };
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
@@ -11,7 +11,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMJoinThreadOperation } from '../../types/dm-ops.js';
+import {
+  type DMJoinThreadOperation,
+  dmJoinThreadOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import {
   messageTruncationStatus,
@@ -206,6 +209,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmJoinThreadOperationValidator,
 });
 
 export { joinThreadSpec };
diff --git a/lib/shared/dm-ops/leave-thread-spec.js b/lib/shared/dm-ops/leave-thread-spec.js
--- a/lib/shared/dm-ops/leave-thread-spec.js
+++ b/lib/shared/dm-ops/leave-thread-spec.js
@@ -8,7 +8,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMLeaveThreadOperation } from '../../types/dm-ops.js';
+import {
+  type DMLeaveThreadOperation,
+  dmLeaveThreadOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { ThickRawThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
 import { minimallyEncodeThreadCurrentUserInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
@@ -192,6 +195,7 @@
     };
   },
   supportsAutoRetry: true,
+  operationValidator: dmLeaveThreadOperationValidator,
 });
 
 export { leaveThreadSpec };
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
@@ -147,6 +147,11 @@
         return;
       }
 
+      if (!dmOpSpecs[dmOp.type].operationValidator.is(dmOp)) {
+        console.log(`Ignoring ${dmOp.type} operation because it is invalid`);
+        return;
+      }
+
       const [messageIDConflictCheckResult, processingCheckResult] =
         await Promise.all([
           checkMessageIDConflict(dmOp, utilities),
diff --git a/lib/shared/dm-ops/remove-members-spec.js b/lib/shared/dm-ops/remove-members-spec.js
--- a/lib/shared/dm-ops/remove-members-spec.js
+++ b/lib/shared/dm-ops/remove-members-spec.js
@@ -7,7 +7,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMRemoveMembersOperation } from '../../types/dm-ops.js';
+import {
+  type DMRemoveMembersOperation,
+  dmRemoveMembersOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { threadTypes } from '../../types/thread-types-enum.js';
 import { updateTypes } from '../../types/update-types-enum.js';
@@ -129,6 +132,7 @@
       };
     },
     supportsAutoRetry: true,
+    operationValidator: dmRemoveMembersOperationValidator,
   });
 
 export { removeMembersSpec };
diff --git a/lib/shared/dm-ops/send-edit-message-spec.js b/lib/shared/dm-ops/send-edit-message-spec.js
--- a/lib/shared/dm-ops/send-edit-message-spec.js
+++ b/lib/shared/dm-ops/send-edit-message-spec.js
@@ -4,7 +4,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMSendEditMessageOperation } from '../../types/dm-ops.js';
+import {
+  type DMSendEditMessageOperation,
+  dmSendEditMessageOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { rawMessageInfoFromMessageData } from '../message-utils.js';
 
@@ -68,6 +71,7 @@
       };
     },
     supportsAutoRetry: true,
+    operationValidator: dmSendEditMessageOperationValidator,
   });
 
 export { sendEditMessageSpec };
diff --git a/lib/shared/dm-ops/send-multimedia-message-spec.js b/lib/shared/dm-ops/send-multimedia-message-spec.js
--- a/lib/shared/dm-ops/send-multimedia-message-spec.js
+++ b/lib/shared/dm-ops/send-multimedia-message-spec.js
@@ -8,9 +8,10 @@
   encryptedMediaBlobURI,
   encryptedVideoThumbnailBlobURI,
 } from '../../media/media-utils.js';
-import type {
-  DMSendMultimediaMessageOperation,
-  DMBlobOperation,
+import {
+  type DMSendMultimediaMessageOperation,
+  type DMBlobOperation,
+  dmSendMultimediaMessageOperationValidator,
 } from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { ClientUpdateInfo } from '../../types/update-types.js';
@@ -101,6 +102,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: false,
+    operationValidator: dmSendMultimediaMessageOperationValidator,
   });
 
 export { sendMultimediaMessageSpec };
diff --git a/lib/shared/dm-ops/send-reaction-message-spec.js b/lib/shared/dm-ops/send-reaction-message-spec.js
--- a/lib/shared/dm-ops/send-reaction-message-spec.js
+++ b/lib/shared/dm-ops/send-reaction-message-spec.js
@@ -4,7 +4,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMSendReactionMessageOperation } from '../../types/dm-ops.js';
+import {
+  type DMSendReactionMessageOperation,
+  dmSendReactionMessageOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { rawMessageInfoFromMessageData } from '../message-utils.js';
 
@@ -76,6 +79,7 @@
       };
     },
     supportsAutoRetry: true,
+    operationValidator: dmSendReactionMessageOperationValidator,
   });
 
 export { sendReactionMessageSpec };
diff --git a/lib/shared/dm-ops/send-text-message-spec.js b/lib/shared/dm-ops/send-text-message-spec.js
--- a/lib/shared/dm-ops/send-text-message-spec.js
+++ b/lib/shared/dm-ops/send-text-message-spec.js
@@ -4,7 +4,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMSendTextMessageOperation } from '../../types/dm-ops.js';
+import {
+  type DMSendTextMessageOperation,
+  dmSendTextMessageOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import type { ClientUpdateInfo } from '../../types/update-types.js';
 import { rawMessageInfoFromMessageData } from '../message-utils.js';
@@ -62,6 +65,7 @@
       return { isProcessingPossible: true };
     },
     supportsAutoRetry: false,
+    operationValidator: dmSendTextMessageOperationValidator,
   });
 
 export { sendTextMessageSpec };
diff --git a/lib/shared/dm-ops/update-relationship-spec.js b/lib/shared/dm-ops/update-relationship-spec.js
--- a/lib/shared/dm-ops/update-relationship-spec.js
+++ b/lib/shared/dm-ops/update-relationship-spec.js
@@ -4,7 +4,10 @@
   DMOperationSpec,
   ProcessDMOperationUtilities,
 } from './dm-op-spec.js';
-import type { DMUpdateRelationshipOperation } from '../../types/dm-ops.js';
+import {
+  type DMUpdateRelationshipOperation,
+  dmUpdateRelationshipOperationValidator,
+} from '../../types/dm-ops.js';
 import { messageTypes } from '../../types/message-types-enum.js';
 import { rawMessageInfoFromMessageData } from '../message-utils.js';
 
@@ -105,6 +108,7 @@
       }
     },
     supportsAutoRetry: true,
+    operationValidator: dmUpdateRelationshipOperationValidator,
   });
 
 export { updateRelationshipSpec };