diff --git a/lib/shared/farcaster/farcaster-messages-types.js b/lib/shared/farcaster/farcaster-messages-types.js
--- a/lib/shared/farcaster/farcaster-messages-types.js
+++ b/lib/shared/farcaster/farcaster-messages-types.js
@@ -11,7 +11,7 @@
   FarcasterDCUserBaseValidator,
   farcasterMessageUserContextValidator,
 } from './farcaster-user-types.js';
-import { tShapeInexact } from '../../utils/validation-utils.js';
+import { tShapeInexact, tFarcasterID } from '../../utils/validation-utils.js';
 
 export const farcasterMessageTypes = Object.freeze({
   TEXT: 'text',
@@ -111,7 +111,7 @@
 };
 const farcasterMessageValidator: TInterface<FarcasterMessage> = tShapeInexact({
   conversationId: t.String,
-  senderFid: t.Number,
+  senderFid: tFarcasterID,
   messageId: t.String,
   serverTimestamp: t.Number,
   type: t.enums.of([
diff --git a/lib/shared/farcaster/farcaster-user-types.js b/lib/shared/farcaster/farcaster-user-types.js
--- a/lib/shared/farcaster/farcaster-user-types.js
+++ b/lib/shared/farcaster/farcaster-user-types.js
@@ -3,7 +3,7 @@
 import type { TInterface } from 'tcomb';
 import t from 'tcomb';
 
-import { tShapeInexact } from '../../utils/validation-utils.js';
+import { tShapeInexact, tFarcasterID } from '../../utils/validation-utils.js';
 
 type FarcasterProfilePicture = {
   +url: string,
@@ -25,7 +25,7 @@
 };
 const farcasterMessageUserContextValidator: TInterface<FarcasterMessageUserContext> =
   tShapeInexact({
-    fid: t.Number,
+    fid: tFarcasterID,
     username: t.maybe(t.String),
     displayName: t.String,
     pfp: t.maybe(farcasterProfilePictureValidator),
@@ -40,7 +40,7 @@
 };
 const FarcasterDCUserBaseValidator: TInterface<FarcasterDCUserBase> =
   tShapeInexact({
-    fid: t.Number,
+    fid: tFarcasterID,
     username: t.maybe(t.String),
     displayName: t.String,
     pfp: t.maybe(farcasterProfilePictureValidator),
@@ -77,7 +77,7 @@
   ...
 };
 const farcasterDCUserValidator: TInterface<FarcasterDCUser> = tShapeInexact({
-  fid: t.Number,
+  fid: tFarcasterID,
   username: t.maybe(t.String),
   displayName: t.String,
   pfp: t.maybe(farcasterProfilePictureValidator),
diff --git a/lib/utils/conversion-utils.js b/lib/utils/conversion-utils.js
--- a/lib/utils/conversion-utils.js
+++ b/lib/utils/conversion-utils.js
@@ -5,7 +5,12 @@
 import type { TInterface, TType } from 'tcomb';
 
 import { convertIDToNewSchema } from './migration-utils.js';
-import { assertWithValidator, tID, tUserID } from './validation-utils.js';
+import {
+  assertWithValidator,
+  tID,
+  tUserID,
+  tFarcasterID,
+} from './validation-utils.js';
 import {
   getPendingThreadID,
   parsePendingThreadID,
@@ -61,14 +66,29 @@
   outputValidator: TType<T>,
   data: T,
 ): $ReadOnlyArray<string> {
-  const result = new Set<string>();
-  const conversionFunction = (id: string) => {
+  return extractIDsFromPayload(outputValidator, data, tUserID);
+}
+
+function extractFarcasterIDsFromPayload<T>(
+  outputValidator: TType<T>,
+  data: T,
+): $ReadOnlyArray<number> {
+  return extractIDsFromPayload(outputValidator, data, tFarcasterID);
+}
+
+function extractIDsFromPayload<T, U>(
+  outputValidator: TType<T>,
+  data: T,
+  extractedType: TType<U>,
+): $ReadOnlyArray<U> {
+  const result = new Set<U>();
+  const conversionFunction = (id: U) => {
     result.add(id);
     return id;
   };
 
   try {
-    convertObject(outputValidator, data, [tUserID], conversionFunction);
+    convertObject(outputValidator, data, [extractedType], conversionFunction);
   } catch {}
 
   return [...result];
@@ -192,6 +212,7 @@
   convertClientIDsToServerIDs,
   convertServerIDsToClientIDs,
   extractUserIDsFromPayload,
+  extractFarcasterIDsFromPayload,
   convertObject,
   convertObjToBytes,
   convertBytesToObj,
diff --git a/lib/utils/validation-utils.js b/lib/utils/validation-utils.js
--- a/lib/utils/validation-utils.js
+++ b/lib/utils/validation-utils.js
@@ -96,6 +96,10 @@
   t.String,
   (id: string) => !!id,
 );
+const tFarcasterID: TRefinement<number> = t.refinement(
+  t.Number,
+  (id: number) => !!id,
+);
 
 const tMediaMessagePhoto: TInterface<PhotoMessageServerDBContent> = tShape({
   type: tString('photo'),
@@ -172,6 +176,7 @@
   tOldValidUsername,
   tID,
   tUserID,
+  tFarcasterID,
   tMediaMessagePhoto,
   tMediaMessageVideo,
   tMediaMessageMedia,