diff --git a/tests/ldap.nix b/tests/ldap.nix
index 5df5580..7a771ad 100644
--- a/tests/ldap.nix
+++ b/tests/ldap.nix
@@ -198,7 +198,10 @@ in
       # to the expected value.
       def test_lookup(postconf_cmdline, key, expected):
         conf = machine.succeed(postconf_cmdline).rstrip()
-        ldap_table_path = re.match('.* =.*ldap:(.*)', conf).group(1)
+        ldap_table_path_match = re.match('.* =.*ldap:(.*)', conf)
+        if not ldap_table_path_match:
+          raise RuntimeError(f"Failed to match LDAP table in '{postconf_cmdline}' response")
+        ldap_table_path = ldap_table_path_match.group(1)
         value = machine.succeed(f"postmap -q {key} ldap:{ldap_table_path}").rstrip()
         try:
           assert value == expected