diff --git a/.circleci/config.yml b/.circleci/config.yml
index 8f1654d..40c6693 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -4,7 +4,7 @@ jobs:
     docker:
       - image: circleci/openjdk:11-jdk-stretch
     steps:
-    - run: sudo apt-get install pkg-config zip g++ zlib1g-dev unzip python
+    - run: sudo apt-get update && sudo apt-get install pkg-config zip g++ zlib1g-dev unzip python
     - run: wget -O /tmp/bazel-installer.sh https://github.com/bazelbuild/bazel/releases/download/0.27.0/bazel-0.27.0-installer-linux-x86_64.sh
     - run: chmod +x /tmp/bazel-installer.sh
     - run: /tmp/bazel-installer.sh --user
diff --git a/tests/BUILD b/tests/BUILD
index 5e45330..156d2f6 100644
--- a/tests/BUILD
+++ b/tests/BUILD
@@ -62,6 +62,33 @@ sh_test(
     ],
 )
 
+generate_codeowners(
+    name = "github_codeowners_auto_sort",
+    owners = [
+        ":py_files",
+        ":multi_team",
+        "//tests/hey/sub/sub2:codeowners",
+        "//tests/hey/sub/sub3:codeowners",
+        "//tests/heyoo:codeowners",
+        "//tests/hey/sub:codeowners",
+        "//tests/hey:codeowners",
+    ],
+    sort = True,
+)
+
+sh_test(
+    name = "validate_codeowners_auto_sort",
+    srcs = ["//tools:diff.sh"],
+    args = [
+        "$(location :github_codeowners_auto_sort.out)",
+        "$(location github_codeowners_auto_sort_golden)",
+    ],
+    data = [
+        "github_codeowners_auto_sort_golden",
+        ":github_codeowners_auto_sort.out",
+    ],
+)
+
 failure_testing_test(
     name = "both_team_and_teams_set",
     expected = "Both team and teams can not be set at the same time.",
diff --git a/tests/github_codeowners_auto_sort_golden b/tests/github_codeowners_auto_sort_golden
new file mode 100644
index 0000000..a58425b
--- /dev/null
+++ b/tests/github_codeowners_auto_sort_golden
@@ -0,0 +1,10 @@
+# This file was generated by rules_codeowners / Bazel
+# Don't edit it directly
+
+/tests/*.html @the-css-team @the-html-team
+/tests/*.py @the-python-dev
+/tests/hey/ @org/foo
+/tests/hey/sub/ @org/foo2
+/tests/hey/sub/sub2/ @org/foo2
+/tests/hey/sub/sub3/ @org/foo2
+/tests/heyoo/*.js @org/bar
diff --git a/tests/hey/sub/sub2/BUILD b/tests/hey/sub/sub2/BUILD
new file mode 100644
index 0000000..1cb243f
--- /dev/null
+++ b/tests/hey/sub/sub2/BUILD
@@ -0,0 +1,7 @@
+load("//tools:codeowners.bzl", "codeowners")
+
+codeowners(
+    name = "codeowners",
+    team = "@org/foo2",
+    visibility = ["//visibility:public"],
+)
diff --git a/tests/hey/sub/sub3/BUILD b/tests/hey/sub/sub3/BUILD
new file mode 100644
index 0000000..1cb243f
--- /dev/null
+++ b/tests/hey/sub/sub3/BUILD
@@ -0,0 +1,7 @@
+load("//tools:codeowners.bzl", "codeowners")
+
+codeowners(
+    name = "codeowners",
+    team = "@org/foo2",
+    visibility = ["//visibility:public"],
+)
diff --git a/tools/codeowners.bzl b/tools/codeowners.bzl
index 5c953bd..799bcf3 100644
--- a/tools/codeowners.bzl
+++ b/tools/codeowners.bzl
@@ -54,12 +54,16 @@ def _generate_codeowners_impl(ctx):
         all_ownerships.append(owner.files.to_list()[0].path)
         all_ownerships_files.append(owner.files.to_list()[0])
 
+    unsorted_tmp_file = ctx.actions.declare_file(ctx.label.name + "_unsorted")
+
     ctx.actions.run_shell(
-        outputs = [ctx.outputs.outfile],
+        outputs = [ctx.outputs.outfile, unsorted_tmp_file],
         inputs = all_ownerships_files,
         arguments = all_ownerships,
         env = {
             "OUTFILE": ctx.outputs.outfile.path,
+            "UNSORTED_FILE": unsorted_tmp_file.path,
+            "SORT": "true" if ctx.attr.sort else "false",
         },
         command = """
 set -euo pipefail
@@ -70,15 +74,23 @@ echo "" >> "$OUTFILE"
 
 for file in "$@"
 do
-    cat "$file" >> "$OUTFILE"
+    cat "$file" >> "$UNSORTED_FILE"
 done
-        """,
+
+# Optional sorting, the most specific rule will appear last in the output
+if "$SORT"; then
+    cat "$UNSORTED_FILE" | sort >> "$OUTFILE"
+else
+    cat "$UNSORTED_FILE" >> "$OUTFILE"
+fi
+""",
     )
 
 generate_codeowners = rule(
     implementation = _generate_codeowners_impl,
     attrs = {
         "owners": attr.label_list(),
+        "sort": attr.bool(default = False, mandatory = False),
     },
     outputs = {
         "outfile": "%{name}.out",