diff --git a/checks/formatting.nix b/checks/formatting.nix
index b399c67..6fde583 100644
--- a/checks/formatting.nix
+++ b/checks/formatting.nix
@@ -4,8 +4,9 @@
 }:
 
 pkgs.runCommand "formatting-check" { } ''
-  ${
-    pkgs.lib.getExe self.formatter.${pkgs.stdenv.hostPlatform.system}
-  } --no-cache --fail-on-change ${../.}
+  cd $(mktemp -d)
+  #mutable copy to make treefmt opening the files with its default mode happy
+  cp ${../.}/* -r ./
+  ${pkgs.lib.getExe self.formatter.${pkgs.stdenv.hostPlatform.system}} --ci --tree-root $PWD ./.
   touch $out
 ''