diff --git a/packaging/hydra.nix b/packaging/hydra.nix
index 6109f479e..e4562cd21 100644
--- a/packaging/hydra.nix
+++ b/packaging/hydra.nix
@@ -18,12 +18,12 @@ let
 
   testNixVersions = pkgs: daemon:
     pkgs.nixComponents.nix-functional-tests.override {
-      pname =
-        "nix-daemon-compat-tests"
-        + lib.optionalString
+      pname = "nix-daemon-compat-tests";
+      version =
+        lib.optionalString
           (lib.versionAtLeast daemon.version "2.4pre20211005" &&
            lib.versionAtLeast pkgs.nix.version "2.4pre20211005")
-          "-${pkgs.nix.version}-with-daemon-${daemon.version}";
+          "${pkgs.nix.version}-with-daemon-${daemon.version}";
 
       test-daemon = daemon;
     };