diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index 472b740d385b..3c5d4fa08ca1 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -155,7 +155,8 @@ main(int argc, char *argv[])
 			while (isalnum(volumelabel[++i]) ||
 			    volumelabel[i] == '_');
 			if (volumelabel[i] != '\0') {
-				errx(1, "bad volume label. Valid characters are alphanumerics.");
+				errx(1, "bad volume label. Valid characters "
+				    "are alphanumerics and underscores.");
 			}
 			if (strlen(volumelabel) >= MAXVOLLEN) {
 				errx(1, "bad volume label. Length is longer than %d.",
diff --git a/sbin/tunefs/tunefs.c b/sbin/tunefs/tunefs.c
index 0bd5f314f4b6..d1f1c36cf787 100644
--- a/sbin/tunefs/tunefs.c
+++ b/sbin/tunefs/tunefs.c
@@ -191,9 +191,8 @@ main(int argc, char *argv[])
 			i = -1;
 			while (isalnum(Lvalue[++i]) || Lvalue[i] == '_');
 			if (Lvalue[i] != '\0') {
-				errx(10,
-				"bad %s. Valid characters are alphanumerics.",
-				    name);
+				errx(10, "bad %s. Valid characters are "
+				    "alphanumerics and underscores.", name);
 			}
 			if (strlen(Lvalue) >= MAXVOLLEN) {
 				errx(10, "bad %s. Length is longer than %d.",