diff --git a/repositories.bzl b/repositories.bzl
index d4378ae..9ce507f 100644
--- a/repositories.bzl
+++ b/repositories.bzl
@@ -98,9 +98,12 @@ def bazel_stardoc():
     maybe(
         http_archive,
         name = "io_bazel_skydoc",
-        url = "https://github.com/bazelbuild/skydoc/archive/0.3.0.tar.gz",
-        sha256 = "c2d66a0cc7e25d857e480409a8004fdf09072a1bd564d6824441ab2f96448eea",
-        strip_prefix = "skydoc-0.3.0",
+        urls = [
+            "https://mirror.bazel.build/github.com/bazelbuild/stardoc/archive/0.4.0.tar.gz",
+            "https://github.com/bazelbuild/stardoc/archive/0.4.0.tar.gz",
+        ],
+        sha256 = "6d07d18c15abb0f6d393adbd6075cd661a2219faab56a9517741f0fc755f6f3c",
+        strip_prefix = "stardoc-0.4.0",
     )
 
 # TODO(fweikert): delete this function if it's not needed by the protobuf project itself.