diff --git a/pkgs/by-name/bo/boinc/package.nix b/pkgs/by-name/bo/boinc/package.nix
index 7d037a93aaf9..4550239740d1 100644
--- a/pkgs/by-name/bo/boinc/package.nix
+++ b/pkgs/by-name/bo/boinc/package.nix
@@ -67,7 +67,9 @@ stdenv.mkDerivation rec {
     xcbutil
   ];
 
-  NIX_LDFLAGS = lib.optionalString (!headless) "-lX11";
+  env = lib.optionalAttrs (!headless) {
+    NIX_LDFLAGS = "-lX11";
+  };
 
   preConfigure = ''
     ./_autosetup