diff --git a/photo21/forms.py b/photo21/forms.py
index 3ab1880..a4cb52b 100644
--- a/photo21/forms.py
+++ b/photo21/forms.py
@@ -17,7 +17,7 @@ class CustomSignupForm(SignupForm):
         """
         Check that the email address ends with a trusted domain.
         """
-        email = self.cleaned_data.get("email")
+        email = super().clean_email()
         if not email.endswith("@crans.org") and not email.endswith("@ens-paris-saclay.fr"):
             raise forms.ValidationError(
                 _("Must end with `@crans.org` or `@ens-paris-saclay.fr`.")