diff --git a/os/access.c b/os/access.c
index 34ebecad9..b1703048d 100644
--- a/os/access.c
+++ b/os/access.c
@@ -581,7 +581,7 @@ static void
 in6_fillscopeid(struct sockaddr_in6 *sin6)
 {
 #if defined(__KAME__)
-    if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr)) {
+    if (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) && sin6->sin6_scope_id == 0) {
         sin6->sin6_scope_id =
             ntohs(*(u_int16_t *) &sin6->sin6_addr.s6_addr[2]);
         sin6->sin6_addr.s6_addr[2] = sin6->sin6_addr.s6_addr[3] = 0;