diff --git a/ihatemoney/forms.py b/ihatemoney/forms.py
index 0e99f534..40b55b58 100644
--- a/ihatemoney/forms.py
+++ b/ihatemoney/forms.py
@@ -248,6 +248,7 @@ class ProjectForm(EditProjectForm):
 class ProjectFormWithCaptcha(ProjectForm):
     captcha = StringField(
         _("Which is a real currency: Euro or Petro dollar?"),
+        default=""
     )
 
     def validate_captcha(form, field):