diff --git a/pkgs/stdenv/adapters.nix b/pkgs/stdenv/adapters.nix
index c1d30b04d48..7ca92b1b2af 100644
--- a/pkgs/stdenv/adapters.nix
+++ b/pkgs/stdenv/adapters.nix
@@ -364,7 +364,7 @@ rec {
       exec 4> >(${pkgs.bzip2}/bin/bzip2 > $out/.trace/log.bz2)
       exec 5> >(${pkgs.coreutils}/bin/tee /dev/fd/4)
       ${pkgs.strace}/bin/strace -e trace=file,process,dup,dup2,close,pipe -v -q -f -s 512 -o /dev/fd/4 ${pkgs.stdenv.shell} -c '(cd $TMPDIR && $builder $realArgs)' 2>&5
-      (cd $out && ${pkgs.gnutar}/bin/tar c .build | ${pkgs.bzip2}/bin/bzip2 > .build.tar.bz2 && ${pkgs.coreutils}/bin/rm -rf .build)
+      (cd $out && ${pkgs.gnutar}/bin/tar c .build | ${pkgs.bzip2}/bin/bzip2 > .build.tar.bz2 && ${pkgs.coreutils}/bin/chmod -R u+w .build && ${pkgs.coreutils}/bin/rm -rf .build)
     '';