diff --git a/README.md b/README.md
index c586e6d..6c82d25 100644
--- a/README.md
+++ b/README.md
@@ -182,6 +182,19 @@ pkgs.fetchFromSteam {
 }
 ```
 
+### [`fetchb4`](./lib/fetchb4)
+
+A fetcher that uses `b4` to download patchsets from <https://lore.kernel.org> so that they can be applied in `boot.kernelPatches`
+
+Usage:
+
+```nix
+pkgs.fetchb4 {
+  msgid = "2024042069.1337-example@example";
+  hash = pkgs.lib.fakeHash;
+}
+```
+
 ### [`mkNginxServer`](./lib/dev-nginx)
 
 creates a shell script that launches nginx in the foreground as the current user. the nginx is
diff --git a/default.nix b/default.nix
index 49798ba..02d6a1a 100644
--- a/default.nix
+++ b/default.nix
@@ -8,6 +8,7 @@
   nixpkgs.overlays = [
     (final: prev: {
       fetchFromSteam = prev.callPackage ./lib/fetchsteam {};
+      fetchb4 = prev.callPackage ./lib/fetchb4 {};
 
       gitSource = prev.callPackage ./lib/git-source {};
 
diff --git a/lib/fetchb4/builder.sh b/lib/fetchb4/builder.sh
new file mode 100644
index 0000000..86f5936
--- /dev/null
+++ b/lib/fetchb4/builder.sh
@@ -0,0 +1,6 @@
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
+source $stdenv/setup
+
+echo "Downloading kernel patch $msgid into $out"
+export HOME="/tmp"
+b4 am -C -o- "$msgid" > "$out"
diff --git a/lib/fetchb4/default.nix b/lib/fetchb4/default.nix
new file mode 100644
index 0000000..2956125
--- /dev/null
+++ b/lib/fetchb4/default.nix
@@ -0,0 +1,15 @@
+{ lib, stdenvNoCC, b4, git, cacert }:
+
+{ msgid, hash }: stdenvNoCC.mkDerivation {
+  name = "patch-${msgid}";
+  builder = ./builder.sh;
+
+  inherit msgid;
+
+  nativeBuildInputs = [ b4 git cacert ];
+  SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
+
+  outputHashMode = "recursive";
+  outputHash = hash;
+  preferLocalBuild = true;
+}