diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix b/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix
new file mode 100644
index 000000000000..58f1a0be8430
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix
@@ -0,0 +1,66 @@
+{
+  mkDerivation,
+  boot-config,
+  pkgsBuildTarget,
+  baseConfig ? "GENERIC",
+}:
+mkDerivation {
+  path = "sys/arch/amd64";
+  pname = "sys";
+  extraPaths = [ "sys" ];
+  noLibc = true;
+
+  extraNativeBuildInputs = [
+    boot-config
+  ];
+
+  postPatch =
+    # The in-kernel debugger (DDB) requires compiler flags not supported by clang, disable it
+    ''
+      sed -E -i -e '/DDB/d' $BSDSRCDIR/sys/conf/GENERIC
+      sed -E -i -e '/pseudo-device\tdt/d' $BSDSRCDIR/sys/arch/amd64/conf/GENERIC
+    ''
+    +
+      # Clang flags compatibility
+      ''
+        find $BSDSRCDIR -name 'Makefile*' -exec sed -E -i -e 's/-fno-ret-protector/-fno-stack-protector/g' -e 's/-nopie/-no-pie/g' {} +
+        sed -E -i -e 's_^\tinstall.*$_\tinstall bsd ''${out}/bsd_' -e s/update-link// $BSDSRCDIR/sys/arch/*/conf/Makefile.*
+      ''
+    +
+      # Remove randomness in build
+      ''
+        sed -E -i -e 's/^PAGE_SIZE=.*$/PAGE_SIZE=4096/g' -e '/^random_uniform/a echo 0; return 0;' $BSDSRCDIR/sys/conf/makegap.sh
+        sed -E -i -e 's/^v=.*$/v=0 u=nixpkgs h=nixpkgs t=`date -d @1`/g' $BSDSRCDIR/sys/conf/newvers.sh
+      '';
+
+  postConfigure = ''
+    export BSDOBJDIR=$TMP/obj
+    mkdir $BSDOBJDIR
+    make obj
+
+    cd conf
+    config ${baseConfig}
+    cd -
+  '';
+
+  preBuild =
+    # A lot of files insist on calling unprefixed GNU `ld` and `objdump`.
+    # It's easier to add them to PATH than patch and substitute.
+    ''
+      mkdir $TMP/bin
+      export PATH=$TMP/bin:$PATH
+      ln -s ${pkgsBuildTarget.binutils}/bin/${pkgsBuildTarget.binutils.targetPrefix}objdump $TMP/bin/objdump
+      ln -s ${pkgsBuildTarget.binutils}/bin/${pkgsBuildTarget.binutils.targetPrefix}ld $TMP/bin/ld
+    ''
+    +
+      # The Makefile claims it needs includes, but it really doesn't.
+      # Tell it includes aren't real and can't hurt it.
+      ''
+        cd compile/${baseConfig}/obj
+        echo 'includes:' >>Makefile
+      '';
+
+  # stand is in a separate package
+  env.SKIPDIR = "stand";
+  env.NIX_CFLAGS_COMPILE = "-Wno-unused-command-line-argument -Wno-visibility";
+}