diff --git a/src/pretix/base/forms/questions.py b/src/pretix/base/forms/questions.py
index 1faec68a4..4d6e4afe4 100644
--- a/src/pretix/base/forms/questions.py
+++ b/src/pretix/base/forms/questions.py
@@ -253,7 +253,7 @@ class NamePartsFormField(forms.MultiValueField):
         if self.require_all_fields and not all(v for v in value):
             raise forms.ValidationError(self.error_messages['incomplete'], code='required')
 
-        if sum(len(v) for v in value if v) > 250:
+        if sum(len(v) for v in value.values() if v) > 250:
             raise forms.ValidationError(_('Please enter a shorter name.'), code='max_length')
 
         return value