diff --git a/pkgs/build-support/kernel/make-initrd.nix b/pkgs/build-support/kernel/make-initrd.nix
index 4b31bf225a48..6f300369aa50 100644
--- a/pkgs/build-support/kernel/make-initrd.nix
+++ b/pkgs/build-support/kernel/make-initrd.nix
@@ -81,12 +81,6 @@ in
     _compressorMeta.ubootName
       or (throw "Unrecognised compressor ${_compressorName}, please specify uInitrdCompression"),
 }:
-let
-  # !!! Move this into a public lib function, it is probably useful for others
-  toValidStoreName =
-    x: with builtins; lib.concatStringsSep "-" (filter (x: !(isList x)) (split "[^a-zA-Z0-9_=.?-]+" x));
-
-in
 stdenvNoCC.mkDerivation (
   rec {
     inherit