diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 3e49bf221087..741c9f8b2b88 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt
@@ -221,6 +221,11 @@ populated with placeholder text.
 	`--subject-prefix` option) has ` v<n>` appended to it.  E.g.
 	`--reroll-count=4` may produce `v4-0001-add-makefile.patch`
 	file that has "Subject: [PATCH v4 1/20] Add makefile" in it.
+	`<n>` does not have to be an integer (e.g. "--reroll-count=4.4",
+	or "--reroll-count=4rev2" are allowed), but the downside of
+	using such a reroll-count is that the range-diff/interdiff
+	with the previous version does not state exactly which
+	version the new interation is compared against.
 
 --to=<email>::
 	Add a `To:` header to the email headers. This is in addition
diff --git a/builtin/log.c b/builtin/log.c
index f67b67d80ed1..af853f111464 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1662,13 +1662,19 @@ static void print_bases(struct base_tree_info *bases, FILE *file)
 	oidclr(&bases->base_commit);
 }
 
-static const char *diff_title(struct strbuf *sb, int reroll_count,
-		       const char *generic, const char *rerolled)
+static const char *diff_title(struct strbuf *sb,
+			      const char *reroll_count,
+			      const char *generic,
+			      const char *rerolled)
 {
-	if (reroll_count <= 0)
+	int v;
+
+	/* RFC may be v0, so allow -v1 to diff against v0 */
+	if (reroll_count && !strtol_i(reroll_count, 10, &v) &&
+	    v >= 1)
+		strbuf_addf(sb, rerolled, v - 1);
+	else
 		strbuf_addstr(sb, generic);
-	else /* RFC may be v0, so allow -v1 to diff against v0 */
-		strbuf_addf(sb, rerolled, reroll_count - 1);
 	return sb->buf;
 }
 
@@ -1717,7 +1723,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct strbuf buf = STRBUF_INIT;
 	int use_patch_format = 0;
 	int quiet = 0;
-	int reroll_count = -1;
+	const char *reroll_count = NULL;
 	char *cover_from_description_arg = NULL;
 	char *branch_name = NULL;
 	char *base_commit = NULL;
@@ -1751,7 +1757,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			    N_("use <sfx> instead of '.patch'")),
 		OPT_INTEGER(0, "start-number", &start_number,
 			    N_("start numbering patches at <n> instead of 1")),
-		OPT_INTEGER('v', "reroll-count", &reroll_count,
+		OPT_STRING('v', "reroll-count", &reroll_count, N_("reroll-count"),
 			    N_("mark the series as Nth re-roll")),
 		OPT_INTEGER(0, "filename-max-length", &fmt_patch_name_max,
 			    N_("max length of output filename")),
@@ -1862,9 +1868,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	if (cover_from_description_arg)
 		cover_from_description_mode = parse_cover_from_description(cover_from_description_arg);
 
-	if (0 < reroll_count) {
+	if (reroll_count) {
 		struct strbuf sprefix = STRBUF_INIT;
-		strbuf_addf(&sprefix, "%s v%d",
+
+		strbuf_addf(&sprefix, "%s v%s",
 			    rev.subject_prefix, reroll_count);
 		rev.reroll_count = reroll_count;
 		rev.subject_prefix = strbuf_detach(&sprefix, NULL);
diff --git a/log-tree.c b/log-tree.c
index 4531cebfab38..f3178a66a95b 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -369,8 +369,14 @@ void fmt_output_subject(struct strbuf *filename,
 	int start_len = filename->len;
 	int max_len = start_len + info->patch_name_max - (strlen(suffix) + 1);
 
-	if (0 < info->reroll_count)
-		strbuf_addf(filename, "v%d-", info->reroll_count);
+	if (info->reroll_count) {
+		struct strbuf temp = STRBUF_INIT;
+
+		strbuf_addf(&temp, "v%s", info->reroll_count);
+		format_sanitized_subject(filename, temp.buf, temp.len);
+		strbuf_addstr(filename, "-");
+		strbuf_release(&temp);
+	}
 	strbuf_addf(filename, "%04d-%s", nr, subject);
 
 	if (max_len < filename->len)
diff --git a/revision.h b/revision.h
index e6be3c845e66..097d08354c61 100644
--- a/revision.h
+++ b/revision.h
@@ -235,7 +235,7 @@ struct rev_info {
 	const char	*mime_boundary;
 	const char	*patch_suffix;
 	int		numbered_files;
-	int		reroll_count;
+	const char	*reroll_count;
 	char		*message_id;
 	struct ident_split from_ident;
 	struct string_list *ref_message_ids;
diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
index 1b26c4c2ef91..e30bc48a2901 100755
--- a/t/t3206-range-diff.sh
+++ b/t/t3206-range-diff.sh
@@ -521,6 +521,30 @@ test_expect_success 'format-patch --range-diff as commentary' '
 	grep "> 1: .* new message" 0001-*
 '
 
+test_expect_success 'format-patch --range-diff reroll-count with a non-integer' '
+	git format-patch --range-diff=HEAD~1 -v2.9 HEAD~1 >actual &&
+	test_when_finished "rm v2.9-0001-*" &&
+	test_line_count = 1 actual &&
+	test_i18ngrep "^Range-diff:$" v2.9-0001-* &&
+	grep "> 1: .* new message" v2.9-0001-*
+'
+
+test_expect_success 'format-patch --range-diff reroll-count with a integer' '
+	git format-patch --range-diff=HEAD~1 -v2 HEAD~1 >actual &&
+	test_when_finished "rm v2-0001-*" &&
+	test_line_count = 1 actual &&
+	test_i18ngrep "^Range-diff ..* v1:$" v2-0001-* &&
+	grep "> 1: .* new message" v2-0001-*
+'
+
+test_expect_success 'format-patch --range-diff with v0' '
+	git format-patch --range-diff=HEAD~1 -v0 HEAD~1 >actual &&
+	test_when_finished "rm v0-0001-*" &&
+	test_line_count = 1 actual &&
+	test_i18ngrep "^Range-diff:$" v0-0001-* &&
+	grep "> 1: .* new message" v0-0001-*
+'
+
 test_expect_success 'range-diff overrides diff.noprefix internally' '
 	git -c diff.noprefix=true range-diff HEAD^...
 '
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index 66630c8413d5..ed0cc8b5e177 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -386,6 +386,30 @@ test_expect_success 'reroll count (-v)' '
 	! grep -v "^Subject: \[PATCH v4 [0-3]/3\] " subjects
 '
 
+test_expect_success 'reroll count (-v) with a fractional number' '
+	rm -fr patches &&
+	git format-patch -o patches --cover-letter -v4.4 main..side >list &&
+	! grep -v "^patches/v4.4-000[0-3]-" list &&
+	sed -n -e "/^Subject: /p" $(cat list) >subjects &&
+	! grep -v "^Subject: \[PATCH v4.4 [0-3]/3\] " subjects
+'
+
+test_expect_success 'reroll (-v) count with a non number' '
+	rm -fr patches &&
+	git format-patch -o patches --cover-letter -v4rev2 main..side >list &&
+	! grep -v "^patches/v4rev2-000[0-3]-" list &&
+	sed -n -e "/^Subject: /p" $(cat list) >subjects &&
+	! grep -v "^Subject: \[PATCH v4rev2 [0-3]/3\] " subjects
+'
+
+test_expect_success 'reroll (-v) count with a non-pathname character' '
+	rm -fr patches &&
+	git format-patch -o patches --cover-letter -v4---..././../--1/.2//  main..side >list &&
+	! grep -v "patches/v4-\.-\.-\.-1-\.2-000[0-3]-" list &&
+	sed -n -e "/^Subject: /p" $(cat list) >subjects &&
+	! grep -v "^Subject: \[PATCH v4---\.\.\./\./\.\./--1/\.2// [0-3]/3\] " subjects
+'
+
 check_threading () {
 	expect="$1" &&
 	shift &&
@@ -2255,6 +2279,16 @@ test_expect_success 'interdiff: reroll-count' '
 	test_i18ngrep "^Interdiff ..* v1:$" v2-0000-cover-letter.patch
 '
 
+test_expect_success 'interdiff: reroll-count with a non-integer' '
+	git format-patch --cover-letter --interdiff=boop~2 -v2.2 -1 boop &&
+	test_i18ngrep "^Interdiff:$" v2.2-0000-cover-letter.patch
+'
+
+test_expect_success 'interdiff: reroll-count with a integer' '
+	git format-patch --cover-letter --interdiff=boop~2 -v2 -1 boop &&
+	test_i18ngrep "^Interdiff ..* v1:$" v2-0000-cover-letter.patch
+'
+
 test_expect_success 'interdiff: solo-patch' '
 	cat >expect <<-\EOF &&
 	  +fleep
