diff --git a/osbase/build/mkucode/spec/BUILD.bazel b/osbase/build/mkucode/spec/BUILD.bazel
new file mode 100644
index 0000000..0210a4b
--- /dev/null
+++ b/osbase/build/mkucode/spec/BUILD.bazel
@@ -0,0 +1,30 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
+
+proto_library(
+    name = "mkucode_proto",
+    srcs = ["spec.proto"],
+    visibility = ["//visibility:public"],
+)
+
+go_proto_library(
+    name = "mkucode_go_proto",
+    importpath = "source.monogon.dev/osbase/build/mkucode",
+    proto = ":mkucode_proto",
+    visibility = ["//visibility:public"],
+)
+
+go_library(
+    name = "spec",
+    embed = [":spec_go_proto"],
+    importpath = "source.monogon.dev/osbase/build/mkucode/spec",
+    visibility = ["//visibility:public"],
+)
+
+go_proto_library(
+    name = "spec_go_proto",
+    importpath = "source.monogon.dev/osbase/build/mkucode/spec",
+    proto = ":mkucode_proto",
+    visibility = ["//visibility:public"],
+)