diff --git a/smash/web/forms/voucher_forms.py b/smash/web/forms/voucher_forms.py
index 6e2e9478a344179910f872e680a5df982bbc3341..725c9ff9eaa75d57d31a0547b8aadd8956e7843f 100644
--- a/smash/web/forms/voucher_forms.py
+++ b/smash/web/forms/voucher_forms.py
@@ -57,6 +57,7 @@ class VoucherForm(ModelForm):
         if instance and instance.pk:
             self.fields['voucher_type'].widget.attrs['readonly'] = True
             self.fields['hours'].widget.attrs['readonly'] = True
+            self.fields['activity_type'].widget.attrs['readonly'] = True
             self.fields['usage_partner'].widget.attrs['readonly'] = True
 
             if instance.status in [VOUCHER_STATUS_USED, VOUCHER_STATUS_EXPIRED]: