--- old/src/java.base/unix/native/libnio/ch/Net.c	2019-03-14 10:36:28.745903098 +0000
+++ new/src/java.base/unix/native/libnio/ch/Net.c	2019-03-14 10:36:28.469903107 +0000
@@ -205,7 +205,7 @@
 
     /* Disable IPV6_V6ONLY to ensure dual-socket support */
     if (domain == AF_INET6) {
-        int arg = 0;
+        int arg = 1;    // V6 only
         if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, (char*)&arg,
                        sizeof(int)) < 0) {
             JNU_ThrowByNameWithLastError(env,