diff --git a/cookbook/forms.py b/cookbook/forms.py
index e47acac0..26e51885 100644
--- a/cookbook/forms.py
+++ b/cookbook/forms.py
@@ -351,8 +351,8 @@ class InviteLinkForm(forms.ModelForm):
 
     def clean(self):
         space = self.cleaned_data['space']
-        if space.max_users != 0 and (UserPreference.objects.filter(space=space).count() + InviteLink.objects.filter(
-                space=space).filter(valid_until__gte=datetime.today()).count()) >= space.max_users:
+        if space.max_users != 0 and (UserPreference.objects.filter(space=space).count() +
+                                     InviteLink.objects.filter(valid_until__gte=datetime.today(), used_by=None, space=space).count()) >= space.max_users:
             raise ValidationError(_('Maximum number of users for this space reached.'))
 
     def clean_email(self):