diff --git a/builtin/log.c b/builtin/log.c
index 634dc782cc..6f9928fabf 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1747,6 +1747,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct commit *commit;
 	struct commit **list = NULL;
 	struct rev_info rev;
+	char *to_free = NULL;
 	struct setup_revision_opt s_r_opt;
 	int nr = 0, total, i;
 	int use_stdout = 0;
@@ -1947,7 +1948,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		strbuf_addch(&buf, '\n');
 	}
 
-	rev.extra_headers = strbuf_detach(&buf, NULL);
+	rev.extra_headers = to_free = strbuf_detach(&buf, NULL);
 
 	if (from) {
 		if (split_ident_line(&rev.from_ident, from, strlen(from)))
@@ -2284,6 +2285,10 @@ done:
 	strbuf_release(&rdiff1);
 	strbuf_release(&rdiff2);
 	strbuf_release(&rdiff_title);
+	free(to_free);
+	if (rev.ref_message_ids)
+		string_list_clear(rev.ref_message_ids, 0);
+	free(rev.ref_message_ids);
 	UNLEAK(rev);
 	return 0;
 }