diff --git a/nixos/tests/clatd.nix b/nixos/tests/clatd.nix
index 1294909cb9ed..91454ab0f723 100644
--- a/nixos/tests/clatd.nix
+++ b/nixos/tests/clatd.nix
@@ -13,8 +13,8 @@
 #        +--|---
 #        | eth2    Address: 2001:db8::1/64
 # Router |
-#        | nat64   Address: 64:ff9b::1/128
-#        |         Route:   64:ff9b::/96
+#        | nat64   Address: fde7:6c52:047e::1/128
+#        |         Route:   fde7:6c52:047e::/96
 #        |         Address: 192.0.2.0/32
 #        |         Route:   192.0.2.0/24
 #        |
@@ -37,11 +37,7 @@
   ];
 
   nodes = {
-    # The server is configured with static IPv4 addresses. RFC 6052 Section 3.1
-    # disallows the mapping of non-global IPv4 addresses like RFC 1918 into the
-    # Well-Known Prefix 64:ff9b::/96. TAYGA also does not allow the mapping of
-    # documentation space (RFC 5737). To circumvent this, 100.64.0.2/24 from
-    # RFC 6589 (Carrier Grade NAT) is used here.
+    # The server is configured with static IPv4 addresses.
     # To reach the IPv4 address pool of the NAT64 gateway, there is a static
     # route configured. In normal cases, where the router would also source NAT
     # the pool addresses to one IPv4 addresses, this would not be needed.
@@ -73,7 +69,7 @@
     # The router is configured with static IPv4 addresses towards the server
     # and IPv6 addresses towards the client. DNS64 is exposed towards the
     # client so clatd is able to auto-discover the PLAT prefix. For NAT64, the
-    # Well-Known prefix 64:ff9b::/96 is used. NAT64 is done with TAYGA which
+    # ULA prefix fde7:6c52:047e::/96 is used. NAT64 is done with TAYGA which
     # provides the tun-interface nat64 and does the translation over it. The
     # IPv6 packets are sent to this interfaces and received as IPv4 packets and
     # vice versa. As TAYGA only translates IPv6 addresses to dedicated IPv4
@@ -121,7 +117,7 @@
       systemd.network.networks."40-eth2" = {
         networkConfig.IPv6SendRA = true;
         ipv6Prefixes = [ { Prefix = "2001:db8::/64"; } ];
-        ipv6PREF64Prefixes = [ { Prefix = "64:ff9b::/96"; } ];
+        ipv6PREF64Prefixes = [ { Prefix = "fde7:6c52:047e::/96"; } ];
         ipv6SendRAConfig = {
           EmitDNS = true;
           DNS = "_link_local";
@@ -141,7 +137,7 @@
           .:53 {
             bind ::
             hosts /etc/hosts
-            dns64 64:ff9b::/96
+            dns64 fde7:6c52:047e::/96
           }
         '';
       };
@@ -161,10 +157,10 @@
         ipv6 = {
           address = "2001:db8::1";
           router = {
-            address = "64:ff9b::1";
+            address = "fde7:6c52:047e::1";
           };
           pool = {
-            address = "64:ff9b::";
+            address = "fde7:6c52:047e::";
             prefixLength = 96;
           };
         };
@@ -221,7 +217,7 @@
     with subtest("networkd exports PREF64 prefix"):
       assert json.loads(client.succeed("networkctl status eth1 --json=short"))[
           "NDisc"
-      ]["PREF64"][0]["Prefix"] == [0x0, 0x64, 0xFF, 0x9B] + ([0] * 12)
+      ]["PREF64"][0]["Prefix"] == [0xfd, 0xe7, 0x6c, 0x52, 0x04, 0x7e] + ([0] * 10)
 
     with subtest("Test ICMP"):
       client.wait_until_succeeds("ping -c3 100.64.0.2 >&2")