diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index f5efc67c9c..b6f4b0eb03 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -29,9 +29,6 @@ static int compare_by_number(const void *a1, const void *a2)
 		return -1;
 }
 
-const char *format_subject(struct strbuf *sb, const char *msg,
-			   const char *line_separator);
-
 static void insert_one_record(struct shortlog *log,
 			      const char *author,
 			      const char *oneline)
diff --git a/commit.h b/commit.h
index 41985130d1..b3c3bb70c5 100644
--- a/commit.h
+++ b/commit.h
@@ -90,6 +90,8 @@ extern char *logmsg_reencode(const struct commit *commit,
 extern char *reencode_commit_message(const struct commit *commit,
 				     const char **encoding_p);
 extern void get_commit_format(const char *arg, struct rev_info *);
+extern const char *format_subject(struct strbuf *sb, const char *msg,
+				  const char *line_separator);
 extern void userformat_find_requirements(const char *fmt, struct userformat_want *w);
 extern void format_commit_message(const struct commit *commit,
 				  const char *format, struct strbuf *sb,