diff --git a/src/pretix/base/forms/questions.py b/src/pretix/base/forms/questions.py
index 717b34266..fa8d36154 100644
--- a/src/pretix/base/forms/questions.py
+++ b/src/pretix/base/forms/questions.py
@@ -550,7 +550,8 @@ class BaseQuestionsForm(forms.Form):
 
         if not self.all_optional:
             for q in question_cache.values():
-                if question_is_required(q) and not d.get('question_%d' % q.pk):
+                answer = d.get('question_%d' % q.pk)
+                if question_is_required(q) and not answer and answer != 0:
                     raise ValidationError({'question_%d' % q.pk: [_('This field is required')]})
 
         return d
diff --git a/src/pretix/presale/checkoutflow.py b/src/pretix/presale/checkoutflow.py
index 5d77533cf..adc770a70 100644
--- a/src/pretix/presale/checkoutflow.py
+++ b/src/pretix/presale/checkoutflow.py
@@ -570,7 +570,7 @@ class QuestionsStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
                 )
 
             for q in cp.item.questions_to_ask:
-                if question_is_required(q) and not answ.get(q.id):
+                if question_is_required(q) and q.id not in answ:
                     if warn:
                         messages.warning(request, _('Please fill in answers to all required questions.'))
                     return False
diff --git a/src/tests/presale/test_checkout.py b/src/tests/presale/test_checkout.py
index 86371f892..1a4134041 100644
--- a/src/tests/presale/test_checkout.py
+++ b/src/tests/presale/test_checkout.py
@@ -2660,7 +2660,7 @@ class QuestionsTestCase(BaseCheckoutTestCase, TestCase):
         # Corrected request
         response = self.client.post('/%s/%s/checkout/questions/' % (self.orga.slug, self.event.slug), {
             '%s-question_%s' % (cr1.id, q1.id): '42',
-            '%s-question_%s' % (cr2.id, q1.id): '23',
+            '%s-question_%s' % (cr2.id, q1.id): '0',
             '%s-question_%s' % (cr1.id, q2.id): 'Internet',
             '%s-question_%s' % (cr2.id, q2.id): '',
             'email': 'admin@localhost'
@@ -2750,6 +2750,7 @@ class QuestionsTestCase(BaseCheckoutTestCase, TestCase):
             event=self.event, question='Why not?', type=Question.TYPE_TEXT,
             required=True, dependency_question=self.q3, dependency_values=['False']
         )
+
         self.ticket.questions.add(self.q1)
         self.ticket.questions.add(self.q2a)
         self.ticket.questions.add(self.q2b)