diff --git a/build/toolchain/protobuf/BUILD.bazel b/build/toolchain/protobuf/BUILD.bazel
new file mode 100644
index 0000000..19caf61
--- /dev/null
+++ b/build/toolchain/protobuf/BUILD.bazel
@@ -0,0 +1,17 @@
+load("@protobuf//bazel/toolchains:proto_toolchain.bzl", "proto_toolchain")
+load(":def.bzl", "ignore_unused_configuration_target")
+
+ignore_unused_configuration_target(
+    name = "protoc",
+    dep = "@protobuf//:protoc",
+    visibility = ["//visibility:private"],
+)
+
+# This is a copy of the toolchain defined at
+# @protobuf//bazel/private/toolchains:protoc_sources_toolchain, but with unused
+# configurations reset, such that we build protoc only once.
+proto_toolchain(
+    name = "protoc_sources",
+    exec_compatible_with = [],
+    proto_compiler = ":protoc",
+)