diff --git a/misc.c b/misc.c
index 1b4b55c50..dd0bd032a 100644
--- a/misc.c
+++ b/misc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.197 2024/09/25 01:24:04 djm Exp $ */
+/* $OpenBSD: misc.c,v 1.198 2024/10/24 03:14:37 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2005-2020 Damien Miller.  All rights reserved.
@@ -2406,7 +2406,8 @@ valid_domain(char *name, int makelower, const char **errstr)
 		strlcpy(errbuf, "empty domain name", sizeof(errbuf));
 		goto bad;
 	}
-	if (!isalpha((u_char)name[0]) && !isdigit((u_char)name[0])) {
+	if (!isalpha((u_char)name[0]) && !isdigit((u_char)name[0]) &&
+	   name[0] != '_' /* technically invalid, but common */) {
 		snprintf(errbuf, sizeof(errbuf), "domain name \"%.100s\" "
 		    "starts with invalid character", name);
 		goto bad;