diff --git a/competition/models.py b/competition/models.py
index 459ac7a..fe3035e 100644
--- a/competition/models.py
+++ b/competition/models.py
@@ -146,7 +146,7 @@ class Meta:
     ]
 
     competition = models.ForeignKey(
-        Competition, null=True, on_delete=models.CASCADE)
+        Competition, on_delete=models.CASCADE)
 
     year = models.PositiveSmallIntegerField(verbose_name='ročník', blank=True)
     school_year = models.CharField(