diff --git a/src/core/dhcp/nm-dhcp-dhclient-utils.c b/src/core/dhcp/nm-dhcp-dhclient-utils.c
index 74e6b9050..72dbc7885 100644
--- a/src/core/dhcp/nm-dhcp-dhclient-utils.c
+++ b/src/core/dhcp/nm-dhcp-dhclient-utils.c
@@ -399,6 +399,7 @@ nm_dhcp_dhclient_create_config(const char         *interface,
                 if (out_new_client_id)
                     nm_clear_pointer(out_new_client_id, g_bytes_unref);
                 NM_SET_OUT(out_new_client_id, read_client_id(p));
+                /* fall-through. We keep the line... */
             }
 
             /* Override config file hostname and use one from the connection */
@@ -656,6 +657,7 @@ nm_dhcp_dhclient_save_duid(const char *leasefile, GBytes *duid, GError **error)
     gsize                         len = 0;
 
     g_return_val_if_fail(leasefile != NULL, FALSE);
+
     if (!duid) {
         nm_utils_error_set_literal(error, NM_UTILS_ERROR_UNKNOWN, "missing duid");
         g_return_val_if_reached(FALSE);
diff --git a/src/core/dhcp/nm-dhcp-dhclient.c b/src/core/dhcp/nm-dhcp-dhclient.c
index 92b4332a7..34aa7d44e 100644
--- a/src/core/dhcp/nm-dhcp-dhclient.c
+++ b/src/core/dhcp/nm-dhcp-dhclient.c
@@ -82,6 +82,10 @@ G_DEFINE_TYPE(NMDhcpDhclient, nm_dhcp_dhclient, NM_TYPE_DHCP_CLIENT)
 
 /*****************************************************************************/
 
+static GBytes *read_duid_from_lease(NMDhcpDhclient *self);
+
+/*****************************************************************************/
+
 static const char *
 nm_dhcp_dhclient_get_path(void)
 {
@@ -332,6 +336,7 @@ static gboolean
 dhclient_start(NMDhcpClient *client,
                gboolean      set_mode,
                gboolean      release,
+               gboolean      set_duid,
                pid_t        *out_pid,
                GError      **error)
 {
@@ -410,8 +415,10 @@ dhclient_start(NMDhcpClient *client,
     }
 
     /* Save the DUID to the leasefile dhclient will actually use */
-    if (addr_family == AF_INET6) {
-        if (!nm_dhcp_dhclient_save_duid(priv->lease_file, client_config->client_id, &local)) {
+    if (set_duid && addr_family == AF_INET6) {
+        if (!nm_dhcp_dhclient_save_duid(priv->lease_file,
+                                        nm_dhcp_client_get_effective_client_id(client),
+                                        &local)) {
             nm_utils_error_set(error,
                                NM_UTILS_ERROR_UNKNOWN,
                                "failed to save DUID to '%s': %s",
@@ -560,6 +567,7 @@ ip6_start(NMDhcpClient *client, const struct in6_addr *ll_addr, GError **error)
     NMDhcpDhclient           *self = NM_DHCP_DHCLIENT(client);
     NMDhcpDhclientPrivate    *priv = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
     const NMDhcpClientConfig *config;
+    gs_unref_bytes GBytes    *effective_client_id = NULL;
 
     config = nm_dhcp_client_get_config(client);
 
@@ -586,7 +594,12 @@ ip6_start(NMDhcpClient *client, const struct in6_addr *ll_addr, GError **error)
         return FALSE;
     }
 
-    return dhclient_start(client, TRUE, FALSE, NULL, error);
+    nm_assert(config->client_id);
+    if (!config->v6.enforce_duid)
+        effective_client_id = read_duid_from_lease(self);
+    nm_dhcp_client_set_effective_client_id(client, effective_client_id ?: config->client_id);
+
+    return dhclient_start(client, TRUE, FALSE, TRUE, NULL, error);
 }
 
 static void
@@ -620,18 +633,18 @@ stop(NMDhcpClient *client, gboolean release)
     if (release) {
         pid_t rpid = -1;
 
-        if (dhclient_start(client, FALSE, TRUE, &rpid, NULL)) {
+        if (dhclient_start(client, FALSE, TRUE, FALSE, &rpid, NULL)) {
             /* Wait a few seconds for the release to happen */
             nm_dhcp_client_stop_pid(rpid, nm_dhcp_client_get_iface(client));
         }
     }
 }
 
-_nm_unused static GBytes *
-get_duid(NMDhcpClient *client)
+static GBytes *
+read_duid_from_lease(NMDhcpDhclient *self)
 {
-    NMDhcpDhclient           *self = NM_DHCP_DHCLIENT(client);
-    NMDhcpDhclientPrivate    *priv = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
+    NMDhcpClient             *client = NM_DHCP_CLIENT(self);
+    NMDhcpDhclientPrivate    *priv   = NM_DHCP_DHCLIENT_GET_PRIVATE(self);
     const NMDhcpClientConfig *client_config;
     GBytes                   *duid      = NULL;
     gs_free char             *leasefile = NULL;