diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index eaf9e157a38..18895ee4d9c 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -232,7 +232,9 @@ static void cleanup_subject(struct strbuf *subject)
 		case 'r': case 'R':
 			if (subject->len <= at + 3)
 				break;
-			if (!memcmp(subject->buf + at + 1, "e:", 2)) {
+			if ((subject->buf[at + 1] == 'e' ||
+			     subject->buf[at + 1] == 'E') &&
+			    subject->buf[at + 2] == ':') {
 				strbuf_remove(subject, at, 3);
 				continue;
 			}