diff --git a/apps/api/v2/src/modules/oauth-clients/controllers/oauth-client-users/oauth-client-users.controller.e2e-spec.ts b/apps/api/v2/src/modules/oauth-clients/controllers/oauth-client-users/oauth-client-users.controller.e2e-spec.ts
index 033a4b86ea..390690526b 100644
--- a/apps/api/v2/src/modules/oauth-clients/controllers/oauth-client-users/oauth-client-users.controller.e2e-spec.ts
+++ b/apps/api/v2/src/modules/oauth-clients/controllers/oauth-client-users/oauth-client-users.controller.e2e-spec.ts
@@ -159,6 +159,21 @@ describe("OAuth Client Users Endpoints", () => {
         .expect(400);
     });
 
+    it(`should fail /POST with incorrect timeFormat`, async () => {
+      const requestBody = {
+        email: userEmail,
+        timeZone: userTimeZone,
+        name: "Alice Smith",
+        timeFormat: 100,
+      };
+
+      await request(app.getHttpServer())
+        .post(`/api/v2/oauth-clients/${oAuthClient.id}/users`)
+        .set("x-cal-secret-key", oAuthClient.secret)
+        .send(requestBody)
+        .expect(400);
+    });
+
     it(`/POST`, async () => {
       const requestBody: CreateManagedUserInput = {
         email: userEmail,
diff --git a/apps/api/v2/src/modules/users/inputs/create-managed-user.input.ts b/apps/api/v2/src/modules/users/inputs/create-managed-user.input.ts
index 7424dfa287..6ee0613300 100644
--- a/apps/api/v2/src/modules/users/inputs/create-managed-user.input.ts
+++ b/apps/api/v2/src/modules/users/inputs/create-managed-user.input.ts
@@ -1,7 +1,7 @@
 import { Locales } from "@/lib/enums/locales";
 import { CapitalizeTimeZone } from "@/lib/inputs/capitalize-timezone";
 import { ApiProperty } from "@nestjs/swagger";
-import { IsOptional, IsTimeZone, IsString, IsEnum } from "class-validator";
+import { IsOptional, IsTimeZone, IsString, IsEnum, IsIn } from "class-validator";
 
 export type WeekDay = "Monday" | "Tuesday" | "Wednesday" | "Thursday" | "Friday" | "Saturday" | "Sunday";
 export type TimeFormat = 12 | 24;
@@ -15,7 +15,8 @@ export class CreateManagedUserInput {
   name!: string;
 
   @IsOptional()
-  @ApiProperty({ example: 12, enum: [12, 24], description: "Must be 12 or 24" })
+  @IsIn([12, 24], { message: "timeFormat must be a number either 12 or 24" })
+  @ApiProperty({ example: 12, enum: [12, 24], description: "Must be a number 12 or 24" })
   timeFormat?: TimeFormat;
 
   @IsOptional()