diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index 59b7e61246bb..7662474ff7aa 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -153,7 +153,8 @@ main(int argc, char *argv[])
 		case 'L':
 			volumelabel = optarg;
 			i = -1;
-			while (isalnum(volumelabel[++i]));
+			while (isalnum(volumelabel[++i]) ||
+			    volumelabel[i] == '_');
 			if (volumelabel[i] != '\0') {
 				errx(1, "bad volume label. Valid characters are alphanumerics.");
 			}