diff --git a/t/t4021-format-patch-signer-mime.sh b/t/t4021-format-patch-signer-mime.sh
new file mode 100755
index 00000000000..67a70fadabb
--- /dev/null
+++ b/t/t4021-format-patch-signer-mime.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+test_description='format-patch -s should force MIME encoding as needed'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+
+	>F &&
+	git add F &&
+	git commit -m initial &&
+	echo new line >F &&
+
+	test_tick &&
+	git commit -m "This adds some lines to F" F
+
+'
+
+test_expect_success 'format normally' '
+
+	git format-patch --stdout -1 >output &&
+	! grep Content-Type output
+
+'
+
+test_expect_success 'format with signoff without funny signer name' '
+
+	git format-patch -s --stdout -1 >output &&
+	! grep Content-Type output
+
+'
+
+test_expect_success 'format with non ASCII signer name' '
+
+	GIT_COMMITTER_NAME="はまの ふにおう" \
+	git format-patch -s --stdout -1 >output &&
+	grep Content-Type output
+
+'
+
+test_done
+