diff --git a/nixos/tests/powerdns.nix b/nixos/tests/powerdns.nix
index 70060bad87b6..d3708d25f0fb 100644
--- a/nixos/tests/powerdns.nix
+++ b/nixos/tests/powerdns.nix
@@ -47,7 +47,9 @@ import ./make-test-python.nix ({ pkgs, lib, ... }: {
     with subtest("Adding an example zone works"):
         # Extract configuration file needed by pdnsutil
         unit = server.succeed("systemctl cat pdns")
-        conf = re.search("(--config-dir=[^ ]+)", unit).group(1)
+        match = re.search("(--config-dir=[^ ]+)", unit)
+        assert(match is not None)
+        conf = match.group(1)
         pdnsutil = "sudo -u pdns pdnsutil " + conf
         server.succeed(f"{pdnsutil} create-zone example.com ns1.example.com")
         server.succeed(f"{pdnsutil} add-record  example.com ns1 A 192.168.1.2")