diff --git a/lib/hx509/ks_dir.c b/lib/hx509/ks_dir.c
index ef07b03ce..a627fc65a 100644
--- a/lib/hx509/ks_dir.c
+++ b/lib/hx509/ks_dir.c
@@ -70,7 +70,7 @@ dir_init(hx509_context context,
 	    return ENOENT;
 	}
 
-	if ((sb.st_mode & S_IFDIR) == 0) {
+	if (!S_ISDIR(sb.st_mode)) {
 	    hx509_set_error_string(context, 0, ENOTDIR,
 				   "%s is not a directory", residue);
 	    return ENOTDIR;