diff --git a/src/dhcp/nm-dhcp-dhclient-utils.c b/src/dhcp/nm-dhcp-dhclient-utils.c
index 4df90d76a0..ae7691f5e8 100644
--- a/src/dhcp/nm-dhcp-dhclient-utils.c
+++ b/src/dhcp/nm-dhcp-dhclient-utils.c
@@ -279,6 +279,7 @@ nm_dhcp_dhclient_create_config (const char *interface,
 
 	g_return_val_if_fail (!anycast_addr || nm_utils_hwaddr_valid (anycast_addr, ETH_ALEN), NULL);
 	g_return_val_if_fail (NM_IN_SET (addr_family, AF_INET, AF_INET6), NULL);
+	nm_assert (!out_new_client_id || !*out_new_client_id);
 
 	new_contents = g_string_new (_("# Created by NetworkManager\n"));
 	fqdn_opts = g_ptr_array_sized_new (5);
@@ -332,6 +333,8 @@ nm_dhcp_dhclient_create_config (const char *interface,
 					continue;
 
 				/* Otherwise capture and return the existing client id */
+				if (out_new_client_id)
+					g_clear_pointer (out_new_client_id, g_bytes_unref);
 				NM_SET_OUT (out_new_client_id, read_client_id (p));
 			}
 
diff --git a/src/dhcp/nm-dhcp-dhclient.c b/src/dhcp/nm-dhcp-dhclient.c
index acb14a014e..f114e92ea9 100644
--- a/src/dhcp/nm-dhcp-dhclient.c
+++ b/src/dhcp/nm-dhcp-dhclient.c
@@ -518,8 +518,10 @@ ip4_start (NMDhcpClient *client, const char *dhcp_anycast_addr, const char *last
 	priv->conf_file = create_dhclient_config (self, AF_INET, iface, uuid, client_id, dhcp_anycast_addr,
 	                                          hostname, timeout, use_fqdn, &new_client_id);
 	if (priv->conf_file) {
-		if (new_client_id)
+		if (new_client_id) {
+			nm_assert (!client_id);
 			nm_dhcp_client_set_client_id (client, new_client_id);
+		}
 		success = dhclient_start (client, NULL, NULL, FALSE, NULL, 0);
 	} else
 		_LOGW ("error creating dhclient configuration file");