diff --git a/sys/net/application_layer/dhcpv6/Kconfig b/sys/net/application_layer/dhcpv6/Kconfig
index 690bf8dd0fb1..23a4db8adf29 100644
--- a/sys/net/application_layer/dhcpv6/Kconfig
+++ b/sys/net/application_layer/dhcpv6/Kconfig
@@ -27,7 +27,7 @@ menuconfig KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
 
 if KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
 
-config CONFIG_DHCPV6_CLIENT_MUD_URL
+config DHCPV6_CLIENT_MUD_URL
     string "URL pointing to a Manufacturer Usage Description file"
 
 endif # KCONFIG_USEMODULE_GNRC_DHCPV6_CLIENT_MUD_URL
diff --git a/sys/net/application_layer/dhcpv6/_dhcpv6.h b/sys/net/application_layer/dhcpv6/_dhcpv6.h
index 6bec53ebdecb..1aff58561f6c 100644
--- a/sys/net/application_layer/dhcpv6/_dhcpv6.h
+++ b/sys/net/application_layer/dhcpv6/_dhcpv6.h
@@ -220,8 +220,8 @@ typedef struct __attribute__((packed)) {
  */
 typedef struct __attribute__((packed)) {
     network_uint16_t type;  /**< @ref DHCPV6_OPT_MUD_URL */
-    network_uint16_t len;   /**< length of the MUDstring in octets. */
-    char mudString[];       /**< MUD URL using the "https" scheme */
+    network_uint16_t len;   /**< length of the mud_string in octets. */
+    char mud_string[];       /**< MUD URL using the "https" scheme */
 } dhcpv6_opt_mud_url_t;
 
 #ifdef __cplusplus
diff --git a/sys/net/application_layer/dhcpv6/client.c b/sys/net/application_layer/dhcpv6/client.c
index cf7fb3f8472a..2fc8461febf2 100644
--- a/sys/net/application_layer/dhcpv6/client.c
+++ b/sys/net/application_layer/dhcpv6/client.c
@@ -85,6 +85,8 @@ static uint32_t transaction_start;
 static uint32_t transaction_id;
 static uint8_t duid_len = sizeof(dhcpv6_duid_l2_t);
 
+static const char mud_url[] = CONFIG_DHCPV6_CLIENT_MUD_URL;
+
 static void _post_solicit_servers(void *args);
 static void _solicit_servers(event_t *event);
 static void _request(event_t *event);
@@ -127,6 +129,10 @@ static void *_thread(void *args)
 void dhcpv6_client_init(event_queue_t *eq, uint16_t netif)
 {
     assert(eq->waiter != NULL);
+    if (IS_USED(MODULE_GNRC_DHCPV6_CLIENT_MUD_URL)) {
+        assert(strlen(mud_url) <= MAX_MUD_URL_LENGTH);
+        assert(strncmp(mud_url, "https://", 8) == 0);
+    }
     event_queue = eq;
     local.netif = netif;
     remote.netif = netif;
@@ -248,18 +254,21 @@ static inline size_t _compose_elapsed_time_opt(dhcpv6_opt_elapsed_time_t *time)
 }
 
 static inline size_t _compose_mud_url_opt(dhcpv6_opt_mud_url_t *mud_url_opt,
-                                          const char *mud_url, size_t len_max)
+                                          size_t len_max)
 {
+    if (!IS_USED(MODULE_GNRC_DHCPV6_CLIENT_MUD_URL)) {
+        return 0;
+    }
     uint16_t len = strlen(mud_url);
 
     if (len > len_max) {
-        assert(0);
+        assert(len <= len_max);
         return 0;
     }
 
     mud_url_opt->type = byteorder_htons(DHCPV6_OPT_MUD_URL);
     mud_url_opt->len = byteorder_htons(len);
-    strncpy(mud_url_opt->mudString, mud_url, len_max);
+    memcpy(mud_url_opt->mud_string, mud_url, len);
     return len + sizeof(dhcpv6_opt_mud_url_t);
 }
 
@@ -729,15 +738,6 @@ static void _solicit_servers(event_t *event)
     msg_len += _compose_elapsed_time_opt(time);
     msg_len += _compose_oro_opt((dhcpv6_opt_oro_t *)&send_buf[msg_len], oro_opts,
                                 ARRAY_SIZE(oro_opts));
-
-    if (IS_USED(MODULE_GNRC_DHCPV6_CLIENT_MUD_URL)) {
-        const char mud_url[] = CONFIG_DHCPV6_CLIENT_MUD_URL;
-        assert(strlen(mud_url) <= MAX_MUD_URL_LENGTH);
-        assert(strncmp(mud_url, "https://", 8) == 0);
-        msg_len += _compose_mud_url_opt((dhcpv6_opt_mud_url_t *)&send_buf[msg_len],
-                                        mud_url, sizeof(send_buf) - msg_len);
-    }
-
     msg_len += _add_ia_pd_from_config(&send_buf[msg_len], sizeof(send_buf) - msg_len);
     DEBUG("DHCPv6 client: send SOLICIT\n");
     _flush_stale_replies(&sock);
@@ -841,6 +841,8 @@ static void _request_renew_rebind(uint8_t type)
     if (type != DHCPV6_REBIND) {
         msg_len += _compose_sid_opt((dhcpv6_opt_duid_t *)&send_buf[msg_len]);
     }
+    msg_len += _compose_mud_url_opt((dhcpv6_opt_mud_url_t *)&send_buf[msg_len],
+                                    sizeof(send_buf) - msg_len);
     transaction_start = _now_cs();
     time = (dhcpv6_opt_elapsed_time_t *)&send_buf[msg_len];
     msg_len += _compose_elapsed_time_opt(time);
diff --git a/tests/gnrc_dhcpv6_client/README.md b/tests/gnrc_dhcpv6_client/README.md
index 90fbe649ca8e..8748fc262d3e 100644
--- a/tests/gnrc_dhcpv6_client/README.md
+++ b/tests/gnrc_dhcpv6_client/README.md
@@ -21,7 +21,7 @@ If you use any platform other than `native`, you need to use `ethos`, otherwise
 `netdev_tap` is chosen.
 
 An instance of Kea that configured via [kea-dhcp6.conf](kea-dhcp6.conf) is
-started in parallel to `make term`/`make test`.
+started in parallel to `make term`/`make test-as-root`.
 
 Read the [Kea documentation] on the configuration file for more information.
 
@@ -31,7 +31,7 @@ If you created your interface and without the script, please reconfigure Kea by
 search & replacing "`tapbr0`" in the configuration file.
 
 ```sh
-BOARD=samr21-xpro make flash test
+BOARD=samr21-xpro make flash test-as-root
 ```
 
 [Kea]: http://kea.isc.org
diff --git a/tests/gnrc_dhcpv6_client_6lbr/README.md b/tests/gnrc_dhcpv6_client_6lbr/README.md
index 31df19686b81..364edafe27c1 100644
--- a/tests/gnrc_dhcpv6_client_6lbr/README.md
+++ b/tests/gnrc_dhcpv6_client_6lbr/README.md
@@ -14,7 +14,7 @@ make flash
 And run the tests using
 
 ```
-sudo make test
+sudo make test-as-root
 ```
 
 Note that root privileges are required since `scapy` needs to construct Ethernet
@@ -24,7 +24,7 @@ The tests succeeds if you see the string `SUCCESS`.
 
 If any problems are encountered (i.e. if the test prints the string `FAILED`),
 set the echo parameter in the `run()` function at the bottom of the test script
-(tests/01-run.py) to `True`. The test script will then offer a more detailed
+(tests-as-root/01-run.py) to `True`. The test script will then offer a more detailed
 output.
 
 [scapy]: https://scapy.readthedocs.io/en/latest/
diff --git a/tests/gnrc_dhcpv6_client_6lbr/tests-as-root/01-run.py b/tests/gnrc_dhcpv6_client_6lbr/tests-as-root/01-run.py
index 0fe215060ad0..28e85b908767 100755
--- a/tests/gnrc_dhcpv6_client_6lbr/tests-as-root/01-run.py
+++ b/tests/gnrc_dhcpv6_client_6lbr/tests-as-root/01-run.py
@@ -129,12 +129,6 @@ def testfunc(child):
     # and it is asking for a prefix delegation
     assert DHCP6OptIA_PD in pkt
 
-    assert DHCP6OptMUD in pkt
-    mud_packet = pkt[DHCP6OptMUD]
-    assert mud_packet.optcode == 112
-    assert mud_packet.optlen == len(MUD_TEST_URL)
-    assert mud_packet.data == MUD_TEST_URL
-
     # reply to solicit with advertise and a prefix provided
     trid = pkt[DHCP6_Solicit].trid
     srv_duid = "aa:bb:cc:dd:ee:ff"
@@ -167,6 +161,12 @@ def testfunc(child):
     # and is still asking for a prefix delegation
     assert DHCP6OptIA_PD in pkt
 
+    assert DHCP6OptMUD in pkt
+    mud_option = pkt[DHCP6OptMUD]
+    assert mud_option.optcode == 112
+    assert mud_option.optlen == len(MUD_TEST_URL)
+    assert mud_option.data == MUD_TEST_URL
+
     # reply to request with reply and a prefix provided
     trid = pkt[DHCP6_Request].trid
     sendp(build_reply_headers(pkt) / DHCP6_Reply(trid=trid) /