diff --git a/competition/models.py b/competition/models.py
index 99da75d..d451a4f 100644
--- a/competition/models.py
+++ b/competition/models.py
@@ -3,6 +3,7 @@
 
 from django.conf import settings
 from django.contrib.sites.models import Site
+from django.core.exceptions import ValidationError
 from django.core.files.storage import FileSystemStorage
 from django.core.validators import validate_slug
 from django.db import models
@@ -236,6 +237,12 @@ class Meta:
         blank=True,
         default=None)
 
+    def clean(self) -> None:
+        if self.season_code == 2:
+            raise ValidationError(
+                'Seminár musí byť zimný alebo letný(season_code 0 alebo 1)')
+        return super().clean()
+
     def save(self, *args, **kwargs) -> None:
         if not self.frozen_results:
             self.frozen_results = None
diff --git a/competition/serializers.py b/competition/serializers.py
index b39c517..c90ce14 100644
--- a/competition/serializers.py
+++ b/competition/serializers.py
@@ -1,6 +1,7 @@
 from django.contrib.auth.models import AnonymousUser
 from django_typomatic import ts_interface
 from rest_framework import serializers
+from rest_framework.exceptions import ValidationError
 
 from competition import models
 from personal.serializers import ProfileShortSerializer, SchoolShortSerializer
@@ -392,6 +393,13 @@ class Meta:
         model = models.Semester
         exclude = ['frozen_results', 'registration_link']
         read_only_fields = ['complete']
+        validators = []
+
+    def validate(self, attrs):
+        if attrs.get('season_code', 0) not in (0, 1):
+            raise ValidationError(
+                'Seminár musí byť zimný alebo letný(season_code 0 alebo 1)')
+        return super().validate(attrs)
 
     def get_complete(self, obj: models.Semester):
         return obj.complete