diff --git a/versions/default.nix b/versions/default.nix
index cec52ce..fb3bade 100644
--- a/versions/default.nix
+++ b/versions/default.nix
@@ -7,5 +7,5 @@ pkgs: ''
   $pg --json s3alfisc summclust > versions/summclust.json
   $pg --json synth-inference synthdid > versions/synthdid.json
   RVER=$( wget -qO- 'https://raw.githubusercontent.com/ropensci/rix/refs/heads/main/inst/extdata/available_df.csv' | tail -n 1 | head -n 1 | cut -d',' -f4 | tr -d '"' )
-  sed -i "s|rixpkgs.url = \"github:rstats-on-nix/nixpkgs/[0-9]\{4\}-[0-9]\{2\}-[0-9]\{2\}\";|rixpkgs.url = \"github:rstats-on-nix/nixpkgs/$RVER\";|" ../flake.nix
+  ${pkgs.gnused}/bin/sed -i "s|rixpkgs.url = \"github:rstats-on-nix/nixpkgs/[0-9]\{4\}-[0-9]\{2\}-[0-9]\{2\}\";|rixpkgs.url = \"github:rstats-on-nix/nixpkgs/$RVER\";|" ../flake.nix
 ''