diff --git a/build/workspace_mirror.bzl b/build/workspace_mirror.bzl
index 5a49129e4d..4922491308 100644
--- a/build/workspace_mirror.bzl
+++ b/build/workspace_mirror.bzl
@@ -39,7 +39,11 @@ def export_urls_impl(repo_ctx):
     repo_ctx.file(repo_ctx.path("BUILD.bazel"), """
 exports_files(glob(["**"]), visibility=["//visibility:public"])
 """)
-    repo_ctx.file(repo_ctx.path("urls.txt"), content = "\n".join(repo_ctx.attr.urls))
+    repo_ctx.file(
+        repo_ctx.path("urls.txt"),
+        # Add a trailing newline, since the "while read" loop needs it
+        content = ("\n".join(repo_ctx.attr.urls) + "\n"),
+    )
 
 _export_urls = repository_rule(
     attrs = {
diff --git a/hack/update-workspace-mirror.sh b/hack/update-workspace-mirror.sh
index 9b7c456c99..98380974cd 100755
--- a/hack/update-workspace-mirror.sh
+++ b/hack/update-workspace-mirror.sh
@@ -19,7 +19,7 @@ set -o nounset
 set -o pipefail
 
 if [[ $# -ne 1 ]]; then
-    echo 'use "bazel run //build:update-mirror"'
+    echo 'use "bazel run //hack:update-mirror"'
     echo "(usage: $0 <file with list of URLs to mirror>)"
     exit 1
 fi