diff --git a/pkgs/tools/security/step-ca/default.nix b/pkgs/tools/security/step-ca/default.nix
index d5d84909f772..8a6cc97ff15d 100644
--- a/pkgs/tools/security/step-ca/default.nix
+++ b/pkgs/tools/security/step-ca/default.nix
@@ -46,6 +46,9 @@ buildGoModule rec {
   # Tests start http servers which need to bind to local addresses:
   # panic: httptest: failed to listen on a port: listen tcp6 [::1]:0: bind: operation not permitted
   __darwinAllowLocalNetworking = true;
+  # Tests need to run in a reproducible order, otherwise they run unreliably on
+  # (at least) x86_64-linux.
+  checkFlags = [ "-p 1" ];
 
   passthru.tests.step-ca = nixosTests.step-ca;