diff --git a/configure b/configure
index f99bafcf0f..d02ece934f 100755
--- a/configure
+++ b/configure
@@ -752,7 +752,6 @@ ISC_PLATFORM_HAVESOCKADDRSTORAGE
 ISC_PLATFORM_HAVEIN6PKTINFO
 ISC_PLATFORM_NEEDIN6ADDRLOOPBACK
 ISC_PLATFORM_NEEDIN6ADDRANY
-ISC_PLATFORM_HAVEINADDR6
 BIND9_CO_RULE
 LIBTOOL_ALLOW_UNDEFINED
 LIBTOOL_MODE_UNINSTALL
@@ -17863,38 +17862,6 @@ See \`config.log' for more details" "$LINENO" 5; }
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for in6_addr" >&5
-$as_echo_n "checking for in6_addr... " >&6; }
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-       #include <sys/types.h>
-       #include <sys/socket.h>
-       #include <netinet/in.h>
-
-int
-main ()
-{
-
-       struct in6_addr in6; return (0);
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-   ISC_PLATFORM_HAVEINADDR6="#undef ISC_PLATFORM_HAVEINADDR6"
-   isc_in_addr6_hack=""
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-   ISC_PLATFORM_HAVEINADDR6="#define ISC_PLATFORM_HAVEINADDR6 1"
-   isc_in_addr6_hack="#define in6_addr in_addr6"
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for in6addr_any" >&5
 $as_echo_n "checking for in6addr_any... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -18051,7 +18018,6 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
 
 
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for struct if_laddrreq" >&5
 $as_echo_n "checking for struct if_laddrreq... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
diff --git a/configure.in b/configure.in
index 31944a7ce8..87cee59ba2 100644
--- a/configure.in
+++ b/configure.in
@@ -1948,24 +1948,6 @@ AC_COMPILE_IFELSE(
   [AC_MSG_RESULT([yes])],
   [AC_MSG_FAILURE([IPv6 support is mandatory])])
 
-AC_MSG_CHECKING([for in6_addr])
-AC_COMPILE_IFELSE(
-  [AC_LANG_PROGRAM(
-     [[
-       #include <sys/types.h>
-       #include <sys/socket.h>
-       #include <netinet/in.h>
-     ]],
-     [[
-       struct in6_addr in6; return (0);
-     ]])],
-  [AC_MSG_RESULT([yes])
-   ISC_PLATFORM_HAVEINADDR6="#undef ISC_PLATFORM_HAVEINADDR6"
-   isc_in_addr6_hack=""],
-  [AC_MSG_RESULT([no])
-   ISC_PLATFORM_HAVEINADDR6="#define ISC_PLATFORM_HAVEINADDR6 1"
-   isc_in_addr6_hack="#define in6_addr in_addr6"])
-
 AC_MSG_CHECKING([for in6addr_any])
 AC_COMPILE_IFELSE(
   [AC_LANG_PROGRAM(
@@ -2043,7 +2025,6 @@ ISC_PLATFORM_HAVESOCKADDRSTORAGE="#define ISC_PLATFORM_HAVESOCKADDRSTORAGE 1"],
 [AC_MSG_RESULT(no)
 ISC_PLATFORM_HAVESOCKADDRSTORAGE="#undef ISC_PLATFORM_HAVESOCKADDRSTORAGE"])
 
-AC_SUBST(ISC_PLATFORM_HAVEINADDR6)
 AC_SUBST(ISC_PLATFORM_NEEDIN6ADDRANY)
 AC_SUBST(ISC_PLATFORM_NEEDIN6ADDRLOOPBACK)
 AC_SUBST(ISC_PLATFORM_HAVEIN6PKTINFO)
diff --git a/lib/isc/include/isc/platform.h.in b/lib/isc/include/isc/platform.h.in
index 3cc5b89e1f..8f5f029d10 100644
--- a/lib/isc/include/isc/platform.h.in
+++ b/lib/isc/include/isc/platform.h.in
@@ -54,12 +54,6 @@
  */
 @ISC_PLATFORM_HAVEIN6PKTINFO@
 
-/*! \brief
- * If this system has in_addr6, rather than in6_addr, ISC_PLATFORM_HAVEINADDR6
- * will be defined.
- */
-@ISC_PLATFORM_HAVEINADDR6@
-
 /*! \brief
  * If this system has sin6_scope_id, ISC_PLATFORM_HAVESCOPEID will be defined.
  */
diff --git a/lib/isc/unix/include/isc/net.h b/lib/isc/unix/include/isc/net.h
index e8ea2dab55..cffd310eac 100644
--- a/lib/isc/unix/include/isc/net.h
+++ b/lib/isc/unix/include/isc/net.h
@@ -80,10 +80,6 @@
 #include <isc/lang.h>
 #include <isc/types.h>
 
-#ifdef ISC_PLATFORM_HAVEINADDR6
-#define in6_addr in_addr6	/*%< Required for pre RFC2133 implementations. */
-#endif
-
 #ifndef IN6ADDR_ANY_INIT
 #ifdef s6_addr
 /*%