diff --git a/backend/src/controllers/answers.ts b/backend/src/controllers/answers.ts
index eaf51749..38cebe84 100644
--- a/backend/src/controllers/answers.ts
+++ b/backend/src/controllers/answers.ts
@@ -1,8 +1,8 @@
 import { Request, Response } from 'express';
-import { requireFields } from './error-helper';
-import { getLearningObjectId, getQuestionId } from './questions';
-import { createAnswer, deleteAnswer, getAnswer, getAnswersByQuestion, updateAnswer } from '../services/answers';
-import { FALLBACK_SEQ_NUM } from '../config';
+import { requireFields } from './error-helper.js';
+import { getLearningObjectId, getQuestionId } from './questions.js';
+import { createAnswer, deleteAnswer, getAnswer, getAnswersByQuestion, updateAnswer } from '../services/answers.js';
+import { FALLBACK_SEQ_NUM } from '../config.js';
 import { AnswerData } from '@dwengo-1/common/interfaces/answer';
 
 export async function getAllAnswersHandler(req: Request, res: Response): Promise<void> {
diff --git a/backend/src/controllers/questions.ts b/backend/src/controllers/questions.ts
index 1158e041..dfb3ef6c 100644
--- a/backend/src/controllers/questions.ts
+++ b/backend/src/controllers/questions.ts
@@ -4,7 +4,7 @@ import { FALLBACK_LANG, FALLBACK_SEQ_NUM, FALLBACK_VERSION_NUM } from '../config
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 import { QuestionData, QuestionId } from '@dwengo-1/common/interfaces/question';
 import { Language } from '@dwengo-1/common/util/language';
-import { requireFields } from './error-helper';
+import { requireFields } from './error-helper.js';
 
 export function getLearningObjectId(hruid: string, version: string, lang: string): LearningObjectIdentifier {
     return {
diff --git a/backend/src/interfaces/answer.ts b/backend/src/interfaces/answer.ts
index b78c579f..513fc63e 100644
--- a/backend/src/interfaces/answer.ts
+++ b/backend/src/interfaces/answer.ts
@@ -1,7 +1,7 @@
 import { mapToQuestionDTO, mapToQuestionDTOId } from './question.js';
 import { Answer } from '../entities/questions/answer.entity.js';
 import { AnswerDTO, AnswerId } from '@dwengo-1/common/interfaces/answer';
-import { mapToTeacherDTO } from './teacher';
+import { mapToTeacherDTO } from './teacher.js';
 
 /**
  * Convert a Question entity to a DTO format.
diff --git a/backend/src/routes/answers.ts b/backend/src/routes/answers.ts
index 5800733a..b74f76a0 100644
--- a/backend/src/routes/answers.ts
+++ b/backend/src/routes/answers.ts
@@ -1,5 +1,5 @@
 import express from 'express';
-import { createAnswerHandler, deleteAnswerHandler, getAnswerHandler, getAllAnswersHandler, updateAnswerHandler } from '../controllers/answers';
+import { createAnswerHandler, deleteAnswerHandler, getAnswerHandler, getAllAnswersHandler, updateAnswerHandler } from '../controllers/answers.js';
 
 const router = express.Router({ mergeParams: true });
 
diff --git a/backend/src/services/answers.ts b/backend/src/services/answers.ts
index f2abad51..ab603883 100644
--- a/backend/src/services/answers.ts
+++ b/backend/src/services/answers.ts
@@ -1,11 +1,11 @@
-import { getAnswerRepository } from '../data/repositories';
-import { Answer } from '../entities/questions/answer.entity';
-import { mapToAnswerDTO, mapToAnswerDTOId } from '../interfaces/answer';
-import { fetchTeacher } from './teachers';
-import { fetchQuestion } from './questions';
+import { getAnswerRepository } from '../data/repositories.js';
+import { Answer } from '../entities/questions/answer.entity.js';
+import { mapToAnswerDTO, mapToAnswerDTOId } from '../interfaces/answer.js';
+import { fetchTeacher } from './teachers.js';
+import { fetchQuestion } from './questions.js';
 import { QuestionId } from '@dwengo-1/common/interfaces/question';
 import { AnswerData, AnswerDTO, AnswerId } from '@dwengo-1/common/interfaces/answer';
-import { NotFoundException } from '../exceptions/not-found-exception';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
 
 export async function getAnswersByQuestion(questionId: QuestionId, full: boolean): Promise<AnswerDTO[] | AnswerId[]> {
     const answerRepository = getAnswerRepository();
diff --git a/backend/src/services/questions.ts b/backend/src/services/questions.ts
index d2e6440e..2dd7da1c 100644
--- a/backend/src/services/questions.ts
+++ b/backend/src/services/questions.ts
@@ -4,9 +4,9 @@ import { Question } from '../entities/questions/question.entity.js';
 import { QuestionRepository } from '../data/questions/question-repository.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
 import { QuestionData, QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
-import { NotFoundException } from '../exceptions/not-found-exception';
-import { FALLBACK_VERSION_NUM } from '../config';
-import { fetchStudent } from './students';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { FALLBACK_VERSION_NUM } from '../config.js';
+import { fetchStudent } from './students.js';
 
 export async function getAllQuestions(id: LearningObjectIdentifier, full: boolean): Promise<QuestionDTO[] | QuestionId[]> {
     const questionRepository: QuestionRepository = getQuestionRepository();