diff --git a/tests/common/server.nix b/tests/common/server.nix
index 561d1bb..1626cc2 100644
--- a/tests/common/server.nix
+++ b/tests/common/server.nix
@@ -2,6 +2,7 @@
   imports = [./../../mailsystem];
   config = {
     virtualisation.memorySize = 1024;
+    virtualisation.cores = lib.mkDefault 2;
     mailsystem = {
       enable = true;
       certificateScheme = "selfsigned";