diff --git a/apps/projection/src/app/data-access/fake-http.service.ts b/apps/projection/src/app/data-access/fake-http.service.ts
index ac12467..e21ce03 100644
--- a/apps/projection/src/app/data-access/fake-http.service.ts
+++ b/apps/projection/src/app/data-access/fake-http.service.ts
@@ -36,7 +36,7 @@ export const randStudent = (): Student => ({
   id: factoryStudent(),
   firstname: randFirstName(),
   lastname: randLastName(),
-  mainTeacher: teachers[randNumber({ max: teachers.length })],
+  mainTeacher: teachers[randNumber({ max: teachers.length - 1 })],
   school: randWord(),
 });