diff --git a/lib/server/titamaapi.dart b/lib/server/titamaapi.dart
index 469737f..0854377 100644
--- a/lib/server/titamaapi.dart
+++ b/lib/server/titamaapi.dart
@@ -37,6 +37,9 @@ class TitamaApi {
 
   @ApiMethod(path: 'courses')
   List<Course> listCourses() {
+    if (_courses.isEmpty) {
+      throw new NotFoundError('Could not find any courses.');
+    }
     return _courses;
   }