diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index b8a927b6b..d1549a4cf 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"))
@@ -375,6 +376,7 @@ class DomainForm(TabForms):
         """
         if "general" in self.instances:
             self.instances["general"].oldname = self.instances["general"].name
+            self.instances["general"].old_dkim_key_length  = self.instances["general"].dkim_key_length
         return super(DomainForm, self).is_valid()
 
     def save(self):
diff --git a/modoboa/admin/handlers.py b/modoboa/admin/handlers.py
index 2159f5dd8..3dfbd609a 100644
--- a/modoboa/admin/handlers.py
+++ b/modoboa/admin/handlers.py
@@ -25,6 +25,10 @@ def update_domain_mxs_and_mailboxes(sender, instance, **kwargs):
         return
     instance.mailbox_set.filter(use_domain_quota=True).update(
         quota=instance.default_mailbox_quota)
+    if instance.old_dkim_key_length != instance.dkim_key_length:
+        instance.dkim_public_key = ""
+        instance.dkim_private_key_path = ""
+        instance.save()
     if instance.old_mail_homes is None:
         return
     qset = (
diff --git a/modoboa/admin/tests/test_domain.py b/modoboa/admin/tests/test_domain.py
index ad985f323..167fd43d4 100644
--- a/modoboa/admin/tests/test_domain.py
+++ b/modoboa/admin/tests/test_domain.py
@@ -432,3 +432,24 @@ 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