diff --git a/pkgs/build-support/kernel/make-initrd.nix b/pkgs/build-support/kernel/make-initrd.nix
index 7ad1affb65a..7a5642e565d 100644
--- a/pkgs/build-support/kernel/make-initrd.nix
+++ b/pkgs/build-support/kernel/make-initrd.nix
@@ -16,10 +16,16 @@
 , name ? "initrd"
 , compressor ? "gzip -9n"
 , prepend ? []
+, lib
 }:
+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));
 
-stdenv.mkDerivation rec {
+in stdenv.mkDerivation rec {
   inherit name;
+
   builder = ./make-initrd.sh;
 
   makeUInitrd = stdenv.hostPlatform.platform.kernelTarget == "uImage";
@@ -36,8 +42,12 @@ stdenv.mkDerivation rec {
   # Note: we don't use closureInfo yet, as that won't build with nix-1.x.
   # See #36268.
   exportReferencesGraph =
-    map (x: [("closure-" + baseNameOf x.symlink) x.object]) contents;
+    lib.zipListsWith 
+      (x: i: [("closure-${toValidStoreName (baseNameOf x.symlink)}-${toString i}") x.object]) 
+      contents 
+      (lib.range 0 (lib.length contents - 1));
   pathsFromGraph = ./paths-from-graph.pl;
 
   inherit compressor prepend;
 }
+