diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index b8a927b6b..737e33b79 100644
--- a/modoboa/admin/forms/domain.py
+++ b/modoboa/admin/forms/domain.py
@@ -53,6 +53,7 @@ class DomainFormGeneral(forms.ModelForm, DynamicForm):
     def __init__(self, user, *args, **kwargs):
         self.oldname = None
         if "instance" in kwargs:
+            self.old_dkim_key_length = kwargs["instance"].dkim_key_length
             self.oldname = kwargs["instance"].name
         super(DomainFormGeneral, self).__init__(*args, **kwargs)
         params = dict(param_tools.get_global_parameters("admin"))
@@ -374,7 +375,8 @@ class DomainForm(TabForms):
 
         """
         if "general" in self.instances:
-            self.instances["general"].oldname = self.instances["general"].name
+            instance = self.instances["general"]
+            instance.oldname = instance.name
         return super(DomainForm, self).is_valid()
 
     def save(self):
diff --git a/modoboa/admin/models/domain.py b/modoboa/admin/models/domain.py
index 5d14044ba..6fc9be1ca 100644
--- a/modoboa/admin/models/domain.py
+++ b/modoboa/admin/models/domain.py
@@ -87,6 +87,7 @@ class Domain(AdminObject):
         super(Domain, self).__init__(*args, **kwargs)
         self.old_mail_homes = None
         self.oldname = self.name
+        self.old_dkim_key_length = self.dkim_key_length
 
     @property
     def domainalias_count(self):
@@ -262,6 +263,9 @@ class Domain(AdminObject):
             self.old_mail_homes = {
                 mb.id: mb.mail_home for mb in self.mailbox_set.all()
             }
+        if self.old_dkim_key_length != self.dkim_key_length:
+            self.dkim_public_key = ""
+            self.dkim_private_key_path = ""       
         super(Domain, self).save(*args, **kwargs)
 
     def delete(self, fromuser, keepdir=False):
diff --git a/modoboa/admin/tests/test_domain.py b/modoboa/admin/tests/test_domain.py
index ad985f323..81c673dcd 100644
--- a/modoboa/admin/tests/test_domain.py
+++ b/modoboa/admin/tests/test_domain.py
@@ -432,3 +432,25 @@ class DKIMTestCase(ModoTestCase):
         response = self.client.get(url)
         self.assertContains(
             response, escape(domain.bind_format_dkim_public_key))
+
+    def test_dkim_key_length_modification(self):
+        """ """
+        self.set_global_parameter("dkim_keys_storage_dir", self.workdir)
+        values = {
+            "name": "pouet.com", "quota": 1000, "default_mailbox_quota": 100,
+            "create_dom_admin": False, "type": "domain", "stepid": "step3",
+            "enable_dkim": True, "dkim_key_selector": "default"
+        }
+        self.ajax_post(reverse("admin:domain_add"), values)
+        call_command("modo", "manage_dkim_keys")
+        key_path = os.path.join(self.workdir, "{}.pem".format(values["name"]))
+        self.assertTrue(os.path.exists(key_path))
+        dom = Domain.objects.get(name="pouet.com")
+        values["dkim_key_length"] = 4096
+        self.ajax_post(reverse("admin:domain_change", args=[dom.pk]), values)
+        dom.refresh_from_db()
+        self.assertEqual(dom.dkim_private_key_path, "")
+        os.unlink(key_path)
+        call_command("modo", "manage_dkim_keys")
+        self.assertTrue(os.path.exists(key_path))
+        
\ No newline at end of file