diff --git a/src/pfwbged/basecontent/types.py b/src/pfwbged/basecontent/types.py
index e1c5e36..c2e1431 100644
--- a/src/pfwbged/basecontent/types.py
+++ b/src/pfwbged/basecontent/types.py
@@ -9,7 +9,7 @@ from collective.dms.mailcontent.dmsmail import IDmsIncomingMail, DmsIncomingMail
 
 from pfwbged.basecontent import _
 
-from .widget import AjaxChosenFieldWidget
+from .widget import AjaxChosenFieldWidget, ReallyAjaxChosenFieldWidget
 
 
 class IPfwbBaseDocument(IDmsDocument):
@@ -30,7 +30,7 @@ class IMedicalCertificate(IDmsIncomingMail):
             title=_(u'Concerned Person'),
             required=True,
             vocabulary='plone.principalsource.Users')
-    form.widget(concerned_person=AjaxChosenFieldWidget)
+    form.widget(concerned_person=ReallyAjaxChosenFieldWidget)
 
 
 class MedicalCertificate(DmsIncomingMail):
diff --git a/src/pfwbged/basecontent/widget.py b/src/pfwbged/basecontent/widget.py
index d3ccc0a..889f0e7 100644
--- a/src/pfwbged/basecontent/widget.py
+++ b/src/pfwbged/basecontent/widget.py
@@ -9,4 +9,13 @@ def AjaxChosenFieldWidget(field, request):
     widget = z3c.form.widget.FieldWidget(field,
         AjaxChosenSelectionWidget(request))
     widget.populate_select = True
+    widget.ignoreMissing = True
+    return widget
+
+@implementer(z3c.form.interfaces.IFieldWidget)
+def ReallyAjaxChosenFieldWidget(field, request):
+    widget = z3c.form.widget.FieldWidget(field,
+        AjaxChosenSelectionWidget(request))
+    widget.populate_select = False
+    widget.ignore_missing = True
     return widget