diff --git a/commit.c b/commit.c
index ef679a0b93..531a666cba 100644
--- a/commit.c
+++ b/commit.c
@@ -1796,7 +1796,8 @@ size_t ignored_log_message_bytes(const char *buf, size_t len)
 		else
 			next_line++;
 
-		if (buf[bol] == comment_line_char || buf[bol] == '\n') {
+		if (starts_with_mem(buf + bol, cutoff - bol, comment_line_str) ||
+		    buf[bol] == '\n') {
 			/* is this the first of the run of comments? */
 			if (!boc)
 				boc = bol;
diff --git a/sequencer.c b/sequencer.c
index 991a2dbe96..664986e3b2 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1840,7 +1840,7 @@ static int is_fixup_flag(enum todo_command command, unsigned flag)
 static void add_commented_lines(struct strbuf *buf, const void *str, size_t len)
 {
 	const char *s = str;
-	while (len > 0 && s[0] == comment_line_char) {
+	while (starts_with_mem(s, len, comment_line_str)) {
 		size_t count;
 		const char *n = memchr(s, '\n', len);
 		if (!n)
@@ -2562,7 +2562,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	/* left-trim */
 	bol += strspn(bol, " \t");
 
-	if (bol == eol || *bol == '\r' || *bol == comment_line_char) {
+	if (bol == eol || *bol == '\r' || starts_with_mem(bol, eol - bol, comment_line_str)) {
 		item->command = TODO_COMMENT;
 		item->commit = NULL;
 		item->arg_offset = bol - buf;
diff --git a/strbuf.c b/strbuf.c
index 7c8f582127..291bdc2a65 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -24,6 +24,17 @@ int istarts_with(const char *str, const char *prefix)
 			return 0;
 }
 
+int starts_with_mem(const char *str, size_t len, const char *prefix)
+{
+	const char *end = str + len;
+	for (; ; str++, prefix++) {
+		if (!*prefix)
+			return 1;
+		else if (str == end || *str != *prefix)
+			return 0;
+	}
+}
+
 int skip_to_optional_arg_default(const char *str, const char *prefix,
 				 const char **arg, const char *def)
 {
diff --git a/strbuf.h b/strbuf.h
index 58dddf2777..3156d6ea8c 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -673,6 +673,7 @@ char *xstrfmt(const char *fmt, ...);
 
 int starts_with(const char *str, const char *prefix);
 int istarts_with(const char *str, const char *prefix);
+int starts_with_mem(const char *str, size_t len, const char *prefix);
 
 /*
  * If the string "str" is the same as the string in "prefix", then the "arg"
diff --git a/trailer.c b/trailer.c
index fe18faf6c5..fdb0b8137e 100644
--- a/trailer.c
+++ b/trailer.c
@@ -882,7 +882,7 @@ static size_t find_trailer_block_start(const char *buf, size_t len)
 
 	/* The first paragraph is the title and cannot be trailers */
 	for (s = buf; s < buf + len; s = next_line(s)) {
-		if (s[0] == comment_line_char)
+		if (starts_with_mem(s, buf + len - s, comment_line_str))
 			continue;
 		if (is_blank_line(s))
 			break;
@@ -902,7 +902,7 @@ static size_t find_trailer_block_start(const char *buf, size_t len)
 		const char **p;
 		ssize_t separator_pos;
 
-		if (bol[0] == comment_line_char) {
+		if (starts_with_mem(bol, buf + len - bol, comment_line_str)) {
 			non_trailer_lines += possible_continuation_lines;
 			possible_continuation_lines = 0;
 			continue;