diff --git a/default.nix b/default.nix
index f108b17..b9059c3 100644
--- a/default.nix
+++ b/default.nix
@@ -7,8 +7,8 @@ stdenv.mkDerivation {
   src = ./.;
 
   postPatch = ''
+    sed -i "2iNIX_BIN_PREFIX=${nixFlakes}/bin/" direnvrc
     substituteInPlace direnvrc \
-      --replace "\''${NIX_BIN_PREFIX:-}" "\''${NIX_BIN_PREFIX:-${nixFlakes}/bin/}" \
       --replace "grep" "${gnugrep}/bin/grep"
   '';
 
diff --git a/direnvrc b/direnvrc
index df5b65b..50141de 100644
--- a/direnvrc
+++ b/direnvrc
@@ -1,6 +1,9 @@
 # shellcheck shell=bash
 
-NIX_BIN_PREFIX=${NIX_BIN_PREFIX:-}
+if [[ -z ${NIX_BIN_PREFIX:-} ]]; then
+  NIX_BIN_PREFIX=$(command -v nix-shell)
+  NIX_BIN_PREFIX="${NIX_BIN_PREFIX%/*}/"
+fi
 
 _nix_export_or_unset() {
   local key=$1 value=$2
@@ -118,12 +121,27 @@ use_flake() {
   _nix_export_or_unset TEMPDIR "$old_tempdir"
 }
 
+_nix_extract_direnv() {
+  local found_direnv
+  found_direnv=0
+  while read -r line; do
+    if [[ "$found_direnv" == "1" ]]; then
+      echo "$line"
+      break
+    elif [[ "$line" == "_____direnv_____" ]]; then
+      found_direnv=1
+    else
+      echo "$line" >&2
+    fi
+  done
+}
+
 use_nix() {
   local path layout_dir
   path=$("${NIX_BIN_PREFIX}nix-instantiate" --find-file nixpkgs)
   layout_dir=$(direnv_layout_dir)
   local experimental_flags=()
-  if nix-shell --experimental-features '' --version 2>/dev/null >&2; then
+  if "${NIX_BIN_PREFIX}nix-shell" --experimental-features '' --version 2>/dev/null >&2; then
     experimental_flags+=('--experimental-features' 'nix-command flakes')
   fi
 
@@ -157,13 +175,12 @@ use_nix() {
   then
     [[ -d "$layout_dir" ]] || mkdir -p "$layout_dir"
     local dump_cmd tmp
-    dump_cmd="echo -n _____direnv_____; \"$direnv\" dump bash"
+    dump_cmd="echo _____direnv_____; \"$direnv\" dump bash"
     tmp=$("${NIX_BIN_PREFIX}nix-shell" \
       "${experimental_flags[@]}" \
       --show-trace --pure "$@" --run "$dump_cmd")
     # show original shell hook output
-    echo "$tmp" | grep -vP '(?<=_____direnv_____).*'
-    echo "$tmp" | grep -oP '(?<=_____direnv_____).*' > "$cache"
+    echo "$tmp" | _nix_extract_direnv >&2 > "$cache"
     update_drv=1
   else
     log_status using cached derivation