diff --git a/nixos/tests/custom-ca.nix b/nixos/tests/custom-ca.nix
index 4480519c7edc..6ed3510dd2cc 100644
--- a/nixos/tests/custom-ca.nix
+++ b/nixos/tests/custom-ca.nix
@@ -82,7 +82,7 @@ in
       # chromium-based browsers refuse to run as root
       test-support.displayManager.auto.user = "alice";
       # browsers may hang with the default memory
-      virtualisation.memorySize = 500;
+      virtualisation.memorySize = 600;
 
       networking.hosts."127.0.0.1" = [ "good.example.com" "bad.example.com" ];
       security.pki.certificateFiles = [ "${example-good-cert}/ca.crt" ];
@@ -162,7 +162,7 @@ in
         browser = command.split()[0]
         with subtest("Good certificate is trusted in " + browser):
             execute_as(
-                "alice", f"env P11_KIT_DEBUG=trust {command} https://good.example.com & >&2"
+                "alice", f"{command} https://good.example.com >&2 &"
             )
             wait_for_window_as("alice", browser)
             machine.wait_for_text("It works!")
@@ -170,9 +170,9 @@ in
             execute_as("alice", "xdotool key ctrl+w")  # close tab
 
         with subtest("Unknown CA is untrusted in " + browser):
-            execute_as("alice", f"{command} https://bad.example.com & >&2")
+            execute_as("alice", f"{command} https://bad.example.com >&2 &")
             machine.wait_for_text(error)
             machine.screenshot("bad" + browser)
-            machine.succeed("pkill " + browser)
+            machine.succeed("pkill -f " + browser)
   '';
 })