diff --git a/src/lib-sieve/sieve-actions.c b/src/lib-sieve/sieve-actions.c
index 629e70e29a01fbeeeb9295f3aed3e857fb80d938..95f875494b0453b81d35ab2d4ac92c4649ddc78b 100644
--- a/src/lib-sieve/sieve-actions.c
+++ b/src/lib-sieve/sieve-actions.c
@@ -1047,7 +1047,7 @@ int sieve_action_reject_mail(const struct sieve_action_exec_env *aenv,
 bool sieve_mailbox_check_name(const char *mailbox, const char **error_r)
 {
 	if (!uni_utf8_str_is_valid(mailbox)) {
-		*error_r = "mailbox is utf-8";
+		*error_r = "invalid utf-8";
 		return FALSE;
 	}
 	return TRUE;