diff --git a/videodinges/admin.py b/videodinges/admin.py
index aee5583..8736f49 100644
--- a/videodinges/admin.py
+++ b/videodinges/admin.py
@@ -1,3 +1,5 @@
+from typing import Iterable
+
 from django import forms
 from django.contrib import admin
 from django.core.exceptions import ValidationError
@@ -17,6 +19,21 @@ class TranscodingsForm(forms.ModelForm):
 			self.add_error('upload', validation_error)
 		return cleaned_data
 
+class TrackInlineFormset(forms.BaseInlineFormSet):
+	forms: Iterable[forms.ModelForm]
+	def clean(self):
+		cleaned_data = super().clean()
+		default_cnt = 0
+		for form in self.forms:
+			try:
+				if form.cleaned_data['default'] is True:
+					default_cnt += 1
+			except AttributeError:
+				pass
+			if default_cnt > 1:
+				form.add_error('default', ValidationError('Can set only one track as default'))
+		return cleaned_data
+
 class TranscodingsInline(admin.StackedInline):
 	model = models.Transcoding
 	form = TranscodingsForm
@@ -25,7 +42,7 @@ class TranscodingsInline(admin.StackedInline):
 
 class TracksInline(admin.StackedInline):
 	model = models.Track
-	#form = TranscodingsForm
+	formset = TrackInlineFormset
 	fields = ('default', 'kind', 'lang', 'label', 'upload')
 	extra = 0