diff --git a/soustredeni/models.py b/soustredeni/models.py
index 9f7269cb..c8b36741 100644
--- a/soustredeni/models.py
+++ b/soustredeni/models.py
@@ -15,6 +15,12 @@ import secrets
 import string
 from django.utils import timezone
 
+def generate_filename_vcf(self, filename):
+	return generate_filename_kontaktnicek(self, filename, 'vcf')
+
+def generate_filemane_pdf(self, filename):
+	return generate_filename_kontaktnicek(self, filename, 'pdf')
+
 def generate_filename_kontaktnicek(self, filename, file_type):
 	# generate random string
 	length = 32
@@ -77,8 +83,8 @@ class Soustredeni(SeminarModelBase):
 	exportovat = models.BooleanField('export do AESOPa', db_column='exportovat', default=False,
 			help_text='Exportuje se jen podle tohoto flagu (ne veřejnosti)')
 	#using lambda to avoid circular import
-	kontaktnicek_vcf = models.FileField('kontaktníček vcf', upload_to=lambda instance, filename: generate_filename_kontaktnicek(instance, filename, 'vcf'), blank=True, null=True)
-	kontaktnicek_pdf = models.FileField('kontaktníček pdf', upload_to=lambda instance, filename: generate_filename_kontaktnicek(instance, filename, 'pdf'), blank=True, null=True)
+	kontaktnicek_vcf = models.FileField('kontaktníček vcf', upload_to=generate_filename_vcf, blank=True, null=True)
+	kontaktnicek_pdf = models.FileField('kontaktníček pdf', upload_to=generate_filemane_pdf, blank=True, null=True)
 	def __str__(self):
 		return '{} ({})'.format(self.misto, self.datum_zacatku)