diff --git a/Endpoint/Controllers/V1/ScheduleController.cs b/Endpoint/Controllers/V1/ScheduleController.cs
index 9057629..bb76a79 100644
--- a/Endpoint/Controllers/V1/ScheduleController.cs
+++ b/Endpoint/Controllers/V1/ScheduleController.cs
@@ -51,7 +51,8 @@ public class ScheduleController(IMediator mediator, IOptionsSnapshot<GeneralConf
         if ((request.Groups == null || request.Groups.Length == 0) &&
             (request.Disciplines == null || request.Disciplines.Length == 0) &&
             (request.Professors == null || request.Professors.Length == 0) &&
-            (request.LectureHalls == null || request.LectureHalls.Length == 0))
+            (request.LectureHalls == null || request.LectureHalls.Length == 0) &&
+            (request.LessonType == null || request.LessonType.Length == 0))
         {
             throw new ControllerArgumentException("At least one of the arguments must be selected."
                               + (request.IsEven.HasValue