diff --git a/pkgs/servers/mail/smtprelay/default.nix b/pkgs/servers/mail/smtprelay/default.nix
index b4dd75a42bd0..8142dc76b98b 100644
--- a/pkgs/servers/mail/smtprelay/default.nix
+++ b/pkgs/servers/mail/smtprelay/default.nix
@@ -16,6 +16,10 @@ buildGoModule rec {
 
   vendorHash = "sha256-assGzM8/APNVVm2vZapPK6sh3tWNTnw6PSFwvEqNDPk=";
 
+  subPackages = [
+    "."
+  ];
+
   CGO_ENABLED = 0;
 
   # We do not supply the build time as the build wouldn't be reproducible otherwise.