diff -urNp -x '*.orig' amanda-3.5.1.org/config/amanda/ipv6.m4 amanda-3.5.1/config/amanda/ipv6.m4
--- amanda-3.5.1.org/config/amanda/ipv6.m4	2017-12-01 14:26:31.000000000 +0100
+++ amanda-3.5.1/config/amanda/ipv6.m4	2021-05-08 10:23:14.050134288 +0200
@@ -70,32 +70,7 @@ AC_DEFUN([AMANDA_CHECK_IPV6],
 	[
 	    case "$host" in
 		*-pc-cygwin) amanda_cv_working_ipv6=no;;
-		*)
-		    AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <sys/types.h>
-#ifdef HAVE_SYS_SOCKET_H
-#include <sys/socket.h>
-#endif
-#ifdef HAVE_NETINET_IN_H
-#include <netinet/in.h>
-#endif
-#ifdef HAVE_WINSOCK2_H
-#include <winsock2.h>
-#endif
-#include <sys/socket.h>
-#include <errno.h>
-
-main()
-{
-   int aa;
-   aa = socket(AF_INET6, SOCK_STREAM, 0);
-   if (aa > 0) return 0;
-   return aa;
-}]])],
-    [ amanda_cv_working_ipv6=yes ],
-    [ amanda_cv_working_ipv6=no ],
-    [ amanda_cv_working_ipv6=yes ]
-		)
+		*) amanda_cv_working_ipv6=yes;;
 	    esac
 	])