diff --git a/t/t9999-test.sh b/t/t9999-test.sh
new file mode 100755
index 0000000000..4c802d5940
--- /dev/null
+++ b/t/t9999-test.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+
+test_description='test'
+
+. ./test-lib.sh
+
+test_expect_success 'file to dir breakage' '
+	>file-to-dir &&
+	# This sorts between "file-to-dir" as a file and "file-to-dir"
+	# as a directory (with the trailing / appended implicitly.
+	>file-to-dir.uh-oh &&
+	git add file-to-dir file-to-dir.uh-oh &&
+	git commit -m "add a file" &&
+
+	# Not "git rm", to preserve "file-to-dir" in the index.
+	rm file-to-dir &&
+	mkdir file-to-dir &&
+	>file-to-dir/file &&
+
+	# It is important to add the file in the directory; adding only
+	# the directory doesnt trigger the bug.
+	git add file-to-dir/file &&
+
+	git diff --cached --no-renames --name-status >actual &&
+
+	cat >expect <<-\EOF &&
+	D	file-to-dir
+	A	file-to-dir/file
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'is it committed as-is?' '
+	git commit -m "replace file with a dir" &&
+	git ls-tree HEAD >actual &&
+
+	# Hardcoded SHA-1 oid :(, because with this bug present
+	# "git rev-parse HEAD:file-to-dir" doesnt show the oid of
+	# the tree, but the oid of the blob that shouldnt be there.
+	cat >expect <<-EOF &&
+	100644 blob $EMPTY_BLOB	file-to-dir.uh-oh
+	040000 tree df2b8fc99e1c1d4dbc0a854d9f72157f1d6ea078	file-to-dir