diff --git a/nixos/tests/coturn.nix b/nixos/tests/coturn.nix
index dff832281c7c..301b34b0da70 100644
--- a/nixos/tests/coturn.nix
+++ b/nixos/tests/coturn.nix
@@ -1,4 +1,4 @@
-import ./make-test-python.nix ({ ... }: {
+import ./make-test-python.nix ({ pkgs, ... }: {
   name = "coturn";
   nodes = {
     default = {
@@ -25,5 +25,9 @@ import ./make-test-python.nix ({ ... }: {
       with subtest("works with static-auth-secret-file"):
           secretsfile.wait_for_unit("coturn.service")
           secretsfile.succeed("grep 'some-very-secret-string' /run/coturn/turnserver.cfg")
+          # Forbidden IP, fails:
+          secretsfile.fail("${pkgs.coturn}/bin/turnutils_uclient -W some-very-secret-string 127.0.0.1 -DgX -e 127.0.0.1 -n 1 -c -y")
+          # allowed-peer-ip, should succeed:
+          secretsfile.succeed("${pkgs.coturn}/bin/turnutils_uclient -W some-very-secret-string 192.168.1.2 -DgX -e 192.168.1.2 -n 1 -c -y")
     '';
 })