diff --git a/builtin-log.c b/builtin-log.c
index d983cbc7bc98f1b28332c18946e5111a6dcba9ab..5c00725f030460ba34c702b9ad31e577ca70d361 100644
--- a/builtin-log.c
+++ b/builtin-log.c
@@ -662,6 +662,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	int i;
 	const char *encoding = "utf-8";
 	struct diff_options opts;
+	int need_8bit_cte = 0;
 
 	if (rev->commit_format != CMIT_FMT_EMAIL)
 		die("Cover letter needs email format");
@@ -672,7 +673,8 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
 	head_sha1 = sha1_to_hex(head->object.sha1);
 
-	log_write_email_headers(rev, head_sha1, &subject_start, &extra_headers);
+	log_write_email_headers(rev, head_sha1, &subject_start, &extra_headers,
+				&need_8bit_cte);
 
 	committer = git_committer_info(0);
 
@@ -681,7 +683,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	pp_user_info(NULL, CMIT_FMT_EMAIL, &sb, committer, DATE_RFC2822,
 		     encoding);
 	pp_title_line(CMIT_FMT_EMAIL, &msg, &sb, subject_start, extra_headers,
-		      encoding, 0);
+		      encoding, need_8bit_cte);
 	pp_remainder(CMIT_FMT_EMAIL, &msg, &sb, 0);
 	printf("%s\n", sb.buf);
 
diff --git a/commit.h b/commit.h
index a1e95914263355e2021f54be4837ed25f1210757..2f63bc8b2fac0d748e13d4435d550d61002092b3 100644
--- a/commit.h
+++ b/commit.h
@@ -70,7 +70,7 @@ extern void pretty_print_commit(enum cmit_fmt fmt, const struct commit*,
                                 struct strbuf *,
                                 int abbrev, const char *subject,
                                 const char *after_subject, enum date_mode,
-				int non_ascii_present);
+				int need_8bit_cte);
 void pp_user_info(const char *what, enum cmit_fmt fmt, struct strbuf *sb,
 		   const char *line, enum date_mode dmode,
 		   const char *encoding);
@@ -80,7 +80,7 @@ void pp_title_line(enum cmit_fmt fmt,
 		   const char *subject,
 		   const char *after_subject,
 		   const char *encoding,
-		   int plain_non_ascii);
+		   int need_8bit_cte);
 void pp_remainder(enum cmit_fmt fmt,
 		  const char **msg_p,
 		  struct strbuf *sb,
diff --git a/log-tree.c b/log-tree.c
index 608f697cf3860245510bff907a643d9b6143e724..5b2963998cc497177d913b6224799531d45dbb4a 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -138,10 +138,14 @@ static int has_non_ascii(const char *s)
 }
 
 void log_write_email_headers(struct rev_info *opt, const char *name,
-			     const char **subject_p, const char **extra_headers_p)
+			     const char **subject_p,
+			     const char **extra_headers_p,
+			     int *need_8bit_cte_p)
 {
 	const char *subject = NULL;
 	const char *extra_headers = opt->extra_headers;
+
+	*need_8bit_cte_p = 0; /* unknown */
 	if (opt->total > 0) {
 		static char buffer[64];
 		snprintf(buffer, sizeof(buffer),
@@ -169,6 +173,7 @@ void log_write_email_headers(struct rev_info *opt, const char *name,
 	if (opt->mime_boundary) {
 		static char subject_buffer[1024];
 		static char buffer[1024];
+		*need_8bit_cte_p = -1; /* NEVER */
 		snprintf(subject_buffer, sizeof(subject_buffer) - 1,
 			 "%s"
 			 "MIME-Version: 1.0\n"
@@ -212,6 +217,7 @@ void show_log(struct rev_info *opt, const char *sep)
 	int abbrev_commit = opt->abbrev_commit ? opt->abbrev : 40;
 	const char *extra;
 	const char *subject = NULL, *extra_headers = opt->extra_headers;
+	int need_8bit_cte = 0;
 
 	opt->loginfo = NULL;
 	if (!opt->verbose_header) {
@@ -255,7 +261,8 @@ void show_log(struct rev_info *opt, const char *sep)
 
 	if (opt->commit_format == CMIT_FMT_EMAIL) {
 		log_write_email_headers(opt, sha1_to_hex(commit->object.sha1),
-					&subject, &extra_headers);
+					&subject, &extra_headers,
+					&need_8bit_cte);
 	} else if (opt->commit_format != CMIT_FMT_USERFORMAT) {
 		fputs(diff_get_color_opt(&opt->diffopt, DIFF_COMMIT), stdout);
 		if (opt->commit_format != CMIT_FMT_ONELINE)
@@ -299,9 +306,11 @@ void show_log(struct rev_info *opt, const char *sep)
 	 * And then the pretty-printed message itself
 	 */
 	strbuf_init(&msgbuf, 0);
+	if (need_8bit_cte >= 0)
+		need_8bit_cte = has_non_ascii(opt->add_signoff);
 	pretty_print_commit(opt->commit_format, commit, &msgbuf,
 			    abbrev, subject, extra_headers, opt->date_mode,
-			    has_non_ascii(opt->add_signoff));
+			    need_8bit_cte);
 
 	if (opt->add_signoff)
 		append_signoff(&msgbuf, opt->add_signoff);
diff --git a/log-tree.h b/log-tree.h
index 0cc9344eabdd0046edf360958376b2037ef643dc..8946ff377ca455dd1c4efaa609ce9af382005836 100644
--- a/log-tree.h
+++ b/log-tree.h
@@ -14,6 +14,8 @@ int log_tree_opt_parse(struct rev_info *, const char **, int);
 void show_log(struct rev_info *opt, const char *sep);
 void show_decorations(struct commit *commit);
 void log_write_email_headers(struct rev_info *opt, const char *name,
-			     const char **subject_p, const char **extra_headers_p);
+			     const char **subject_p,
+			     const char **extra_headers_p,
+			     int *need_8bit_cte_p);
 
 #endif
diff --git a/pretty.c b/pretty.c
index 703f52176bf0b5cbf52cf1f77ba55ba6d87fac94..16bfb86cd3ce6d6b471cdc313114563ca78837dc 100644
--- a/pretty.c
+++ b/pretty.c
@@ -636,7 +636,7 @@ void pp_title_line(enum cmit_fmt fmt,
 		   const char *subject,
 		   const char *after_subject,
 		   const char *encoding,
-		   int plain_non_ascii)
+		   int need_8bit_cte)
 {
 	struct strbuf title;
 
@@ -669,7 +669,7 @@ void pp_title_line(enum cmit_fmt fmt,
 	}
 	strbuf_addch(sb, '\n');
 
-	if (plain_non_ascii) {
+	if (need_8bit_cte > 0) {
 		const char *header_fmt =
 			"MIME-Version: 1.0\n"
 			"Content-Type: text/plain; charset=%s\n"
@@ -718,9 +718,9 @@ void pp_remainder(enum cmit_fmt fmt,
 }
 
 void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
-				  struct strbuf *sb, int abbrev,
-				  const char *subject, const char *after_subject,
-				  enum date_mode dmode, int plain_non_ascii)
+			 struct strbuf *sb, int abbrev,
+			 const char *subject, const char *after_subject,
+			 enum date_mode dmode, int need_8bit_cte)
 {
 	unsigned long beginning_of_body;
 	int indent = 4;
@@ -746,13 +746,11 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 	if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
 		indent = 0;
 
-	/* After-subject is used to pass in Content-Type: multipart
-	 * MIME header; in that case we do not have to do the
-	 * plaintext content type even if the commit message has
-	 * non 7-bit ASCII character.  Otherwise, check if we need
-	 * to say this is not a 7-bit ASCII.
+	/*
+	 * We need to check and emit Content-type: to mark it
+	 * as 8-bit if we haven't done so.
 	 */
-	if (fmt == CMIT_FMT_EMAIL && !after_subject) {
+	if (fmt == CMIT_FMT_EMAIL && need_8bit_cte == 0) {
 		int i, ch, in_body;
 
 		for (in_body = i = 0; (ch = msg[i]); i++) {
@@ -765,7 +763,7 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 					in_body = 1;
 			}
 			else if (non_ascii(ch)) {
-				plain_non_ascii = 1;
+				need_8bit_cte = 1;
 				break;
 			}
 		}
@@ -790,7 +788,7 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 	/* These formats treat the title line specially. */
 	if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
 		pp_title_line(fmt, &msg, sb, subject,
-			      after_subject, encoding, plain_non_ascii);
+			      after_subject, encoding, need_8bit_cte);
 
 	beginning_of_body = sb->len;
 	if (fmt != CMIT_FMT_ONELINE)
diff --git a/t/t4021-format-patch-signer-mime.sh b/t/t4021-format-patch-signer-mime.sh
index 67a70fadabbdcaca15832c86d76f1e194a923a75..ba43f185494630c50fc2a168df8dcd45c0b2421b 100755
--- a/t/t4021-format-patch-signer-mime.sh
+++ b/t/t4021-format-patch-signer-mime.sh
@@ -32,11 +32,19 @@ test_expect_success 'format with signoff without funny signer name' '
 
 test_expect_success 'format with non ASCII signer name' '
 
-	GIT_COMMITTER_NAME="$B$O$^$N(B $B$U$K$*$&(B" \
+	GIT_COMMITTER_NAME="はまの ふにおう" \
 	git format-patch -s --stdout -1 >output &&
 	grep Content-Type output
 
 '
 
+test_expect_success 'attach and signoff do not duplicate mime headers' '
+
+	GIT_COMMITTER_NAME="はまの ふにおう" \
+	git format-patch -s --stdout -1 --attach >output &&
+	test `grep -ci ^MIME-Version: output` = 1
+
+'
+
 test_done
 
diff --git a/t/t4028-format-patch-mime-headers.sh b/t/t4028-format-patch-mime-headers.sh
new file mode 100755
index 0000000000000000000000000000000000000000..204ba673cb58f905f2f35ff5b83294b2a2943f48
--- /dev/null
+++ b/t/t4028-format-patch-mime-headers.sh
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+test_description='format-patch mime headers and extra headers do not conflict'
+. ./test-lib.sh
+
+test_expect_success 'create commit with utf-8 body' '
+	echo content >file &&
+	git add file &&
+	git commit -m one &&
+	echo more >>file &&
+	git commit -a -m "two
+
+	utf-8 body: ñ"
+'
+
+test_expect_success 'patch has mime headers' '
+	rm -f 0001-two.patch &&
+	git format-patch HEAD^ &&
+	grep -i "content-type: text/plain; charset=utf-8" 0001-two.patch
+'
+
+test_expect_success 'patch has mime and extra headers' '
+	rm -f 0001-two.patch &&
+	git config format.headers "x-foo: bar" &&
+	git format-patch HEAD^ &&
+	grep -i "x-foo: bar" 0001-two.patch &&
+	grep -i "content-type: text/plain; charset=utf-8" 0001-two.patch
+'
+
+test_done