diff --git a/pkgs/tools/package-management/nix/default.nix b/pkgs/tools/package-management/nix/default.nix
index 07c130f1cb3..5c8341941ed 100644
--- a/pkgs/tools/package-management/nix/default.nix
+++ b/pkgs/tools/package-management/nix/default.nix
@@ -71,7 +71,9 @@ let
     doInstallCheck = true; # not cross
 
     # socket path becomes too long otherwise
-    preInstallCheck = lib.optional stdenv.isDarwin "export TMPDIR=/tmp";
+    preInstallCheck = lib.optional stdenv.isDarwin ''
+      export TMPDIR=$NIX_BUILD_TOP
+    '';
 
     separateDebugInfo = stdenv.isLinux;