diff --git a/packages/backend-common/src/middleware/errorHandler.test.ts b/packages/backend-common/src/middleware/errorHandler.test.ts
index a7a3d64bd1..6d22c2f175 100644
--- a/packages/backend-common/src/middleware/errorHandler.test.ts
+++ b/packages/backend-common/src/middleware/errorHandler.test.ts
@@ -72,6 +72,9 @@ describe('errorHandler', () => {
 
   it('handles well-known error classes', async () => {
     const app = express();
+    app.use('/NotModifiedError', () => {
+      throw new errors.NotModifiedError();
+    });
     app.use('/InputError', () => {
       throw new errors.InputError();
     });
@@ -90,6 +93,7 @@ describe('errorHandler', () => {
     app.use(errorHandler());
 
     const r = request(app);
+    expect((await r.get('/NotModifiedError')).status).toBe(304);
     expect((await r.get('/InputError')).status).toBe(400);
     expect((await r.get('/AuthenticationError')).status).toBe(401);
     expect((await r.get('/NotAllowedError')).status).toBe(403);
diff --git a/packages/backend-common/src/middleware/errorHandler.ts b/packages/backend-common/src/middleware/errorHandler.ts
index 7365ce8b93..a08849813d 100644
--- a/packages/backend-common/src/middleware/errorHandler.ts
+++ b/packages/backend-common/src/middleware/errorHandler.ts
@@ -101,6 +101,8 @@ function getStatusCode(error: Error): number {
 
   // Handle well-known error types
   switch (error.name) {
+    case errors.NotModifiedError.name:
+      return 304;
     case errors.InputError.name:
       return 400;
     case errors.AuthenticationError.name: