diff --git a/python/proto/BUILD.bazel b/python/proto/BUILD.bazel
index 9f60574f26..4d5a92a93f 100644
--- a/python/proto/BUILD.bazel
+++ b/python/proto/BUILD.bazel
@@ -14,5 +14,11 @@
 
 package(default_visibility = ["//visibility:public"])
 
-# Toolchain type provided by proto_lang_toolchain rule and used by py_proto_library
-toolchain_type(name = "toolchain_type")
+# Deprecated; use @com_google_protobuf//bazel/private:python_toolchain_type instead.
+# Alias is here to provide backward-compatibility; see #2604
+# It will be removed in a future release.
+alias(
+    name = "toolchain_type",
+    actual = "@com_google_protobuf//bazel/private:python_toolchain_type",
+    deprecation = "Use @com_google_protobuf//bazel/private:python_toolchain_type instead",
+)