diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 9a4db84f7b73..26c1197bf975 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -630,7 +630,7 @@ in
 
       boot.loader.grub.extraPrepareConfig =
         concatStrings (mapAttrsToList (n: v: ''
-          ${pkgs.coreutils}/bin/cp -pf "${v}" "/boot/${n}"
+          ${pkgs.coreutils}/bin/cp -pf "${v}" "@bootPath@/${n}"
         '') config.boot.loader.grub.extraFiles);
 
       assertions = [
diff --git a/nixos/modules/system/boot/loader/grub/install-grub.pl b/nixos/modules/system/boot/loader/grub/install-grub.pl
index a09c5dc47618..ca0fb0248e0e 100644
--- a/nixos/modules/system/boot/loader/grub/install-grub.pl
+++ b/nixos/modules/system/boot/loader/grub/install-grub.pl
@@ -475,6 +475,9 @@ if ($grubVersion == 2) {
     }
 }
 
+# extraPrepareConfig could refer to @bootPath@, which we have to substitute
+$extraPrepareConfig =~ s/\@bootPath\@/$bootPath/g;
+
 # Run extraPrepareConfig in sh
 if ($extraPrepareConfig ne "") {
   system((get("shell"), "-c", $extraPrepareConfig));