diff --git a/tests/internal.nix b/tests/internal.nix
index a22a67d..8fccbfb 100644
--- a/tests/internal.nix
+++ b/tests/internal.nix
@@ -36,5 +36,15 @@ pkgs.nixosTest {
         machine.succeed(
             "${pkgs.postfix}/bin/postfix check"
         )
+
+    with subtest("vmail uid is set correctly"):
+        machine.succeed(
+            "[ $(getent passwd vmail | cut -d: -f3) -eq 5000 ]"
+        )
+
+    with subtest("vmail gid is set correctly"):
+        machine.succeed(
+            "[ $(getent group vmail | cut -d: -f3) -eq 5000 ]"
+        )
   '';
 }