diff --git a/seminar/migrations/0002_treenode_polymorphic_ctype.py b/seminar/migrations/0002_treenode_polymorphic_ctype.py
deleted file mode 100644
index 4398be6c..00000000
--- a/seminar/migrations/0002_treenode_polymorphic_ctype.py
+++ /dev/null
@@ -1,20 +0,0 @@
-# Generated by Django 2.2.4 on 2019-08-13 19:36
-
-from django.db import migrations, models
-import django.db.models.deletion
-
-
-class Migration(migrations.Migration):
-
-    dependencies = [
-        ('contenttypes', '0002_remove_content_type_name'),
-        ('seminar', '0001_initial'),
-    ]
-
-    operations = [
-        migrations.AddField(
-            model_name='treenode',
-            name='polymorphic_ctype',
-            field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_seminar.treenode_set+', to='contenttypes.ContentType'),
-        ),
-    ]
diff --git a/seminar/migrations/0003_problem_polymorphic_ctype.py b/seminar/migrations/0003_problem_polymorphic_ctype.py
deleted file mode 100644
index 279efbf4..00000000
--- a/seminar/migrations/0003_problem_polymorphic_ctype.py
+++ /dev/null
@@ -1,20 +0,0 @@
-# Generated by Django 2.2.4 on 2019-08-13 19:45
-
-from django.db import migrations, models
-import django.db.models.deletion
-
-
-class Migration(migrations.Migration):
-
-    dependencies = [
-        ('contenttypes', '0002_remove_content_type_name'),
-        ('seminar', '0002_treenode_polymorphic_ctype'),
-    ]
-
-    operations = [
-        migrations.AddField(
-            model_name='problem',
-            name='polymorphic_ctype',
-            field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_seminar.problem_set+', to='contenttypes.ContentType'),
-        ),
-    ]
diff --git a/seminar/migrations/0065_treenode_polymorphic_ctype.py b/seminar/migrations/0065_treenode_polymorphic_ctype.py
new file mode 100644
index 00000000..71eef262
--- /dev/null
+++ b/seminar/migrations/0065_treenode_polymorphic_ctype.py
@@ -0,0 +1,31 @@
+# Generated by Django 2.2.4 on 2019-08-13 19:36
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+def vyrob_treenodum_ctypes(apps, schema_editor):
+	# Kód zkopírovaný z dokumentace: https://django-polymorphic.readthedocs.io/en/stable/migrating.html
+	# XXX: Nevím, jestli se tohle náhodou nemělo spustit na všech childech (jen/i)
+	TreeNode = apps.get_model('seminar', 'TreeNode')
+	ContentType = apps.get_model('contenttypes', 'ContentType')
+	
+	new_ct = ContentType.objects.get_for_model(TreeNode)
+	TreeNode.objects.filter(polymorphic_ctype__isnull=True).update(polymorphic_ctype=new_ct)
+
+
+
+class Migration(migrations.Migration):
+	
+	dependencies = [
+		('contenttypes', '0002_remove_content_type_name'),
+		('seminar', '0064_auto_20190610_2358'),
+	]
+	
+	operations = [
+		migrations.AddField(
+			model_name='treenode',
+			name='polymorphic_ctype',
+			field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_seminar.treenode_set+', to='contenttypes.ContentType'),
+		),
+		migrations.RunPython(vyrob_treenodum_ctypes, migrations.RunPython.noop),
+	]
diff --git a/seminar/migrations/0066_problem_polymorphic_ctype.py b/seminar/migrations/0066_problem_polymorphic_ctype.py
new file mode 100644
index 00000000..f956217e
--- /dev/null
+++ b/seminar/migrations/0066_problem_polymorphic_ctype.py
@@ -0,0 +1,29 @@
+# Generated by Django 2.2.4 on 2019-08-13 19:45
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+def vyrob_problemum_ctypes(apps, schema_editor):
+	# Kód zkopírovaný z dokumentace: https://django-polymorphic.readthedocs.io/en/stable/migrating.html
+	# XXX: Nevím, jestli se tohle náhodou nemělo spustit na všech childech (jen/i)
+	Problem = apps.get_model('seminar', 'Problem')
+	ContentType = apps.get_model('contenttypes', 'ContentType')
+	
+	new_ct = ContentType.objects.get_for_model(Problem)
+	Problem.objects.filter(polymorphic_ctype__isnull=True).update(polymorphic_ctype=new_ct)
+
+class Migration(migrations.Migration):
+	
+	dependencies = [
+		('contenttypes', '0002_remove_content_type_name'),
+		('seminar', '0065_treenode_polymorphic_ctype'),
+	]
+	
+	operations = [
+		migrations.AddField(
+			model_name='problem',
+			name='polymorphic_ctype',
+			field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_seminar.problem_set+', to='contenttypes.ContentType'),
+		),
+		migrations.RunPython(vyrob_problemum_ctypes, migrations.RunPython.noop),
+	]