diff --git a/configure b/configure
index ab066f90..68553361 100755
--- a/configure
+++ b/configure
@@ -1754,6 +1754,52 @@ $as_echo "$ac_res" >&6; }
 
 } # ac_fn_c_check_func
 
+# ac_fn_c_check_decl LINENO SYMBOL VAR INCLUDES
+# ---------------------------------------------
+# Tests whether SYMBOL is declared in INCLUDES, setting cache variable VAR
+# accordingly.
+ac_fn_c_check_decl ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  as_decl_name=`echo $2|sed 's/ *(.*//'`
+  as_decl_use=`echo $2|sed -e 's/(/((/' -e 's/)/) 0&/' -e 's/,/) 0& (/g'`
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $as_decl_name is declared" >&5
+$as_echo_n "checking whether $as_decl_name is declared... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+$4
+int
+main ()
+{
+#ifndef $as_decl_name
+#ifdef __cplusplus
+  (void) $as_decl_use;
+#else
+  (void) $as_decl_name;
+#endif
+#endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_c_check_decl
+
 # ac_fn_c_check_type LINENO TYPE VAR INCLUDES
 # -------------------------------------------
 # Tests whether TYPE exists after having included INCLUDES, setting cache
@@ -10797,9 +10843,16 @@ fi
 
 case "$enable_tcp_fastopen" in
 	yes)
-		# TODO: Check if it is available (linux only)
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: TCP Fast Open enabled" >&5
-$as_echo "$as_me: TCP Fast Open enabled" >&6;}
+		ac_fn_c_check_decl "$LINENO" "MSG_FASTOPEN" "ac_cv_have_decl_MSG_FASTOPEN" "$ac_includes_default
+#include <sys/socket.h>
+
+"
+if test "x$ac_cv_have_decl_MSG_FASTOPEN" = xyes; then :
+
+else
+  as_fn_error $? "TCP Fast Open is not available: please rerun without --enable-tcp-fastopen" "$LINENO" 5
+fi
+
 
 cat >>confdefs.h <<_ACEOF
 #define USE_TCP_FASTOPEN 1
@@ -10807,8 +10860,6 @@ _ACEOF
 
 		;;
 	no|*)
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: TCP Fast Open not enabled" >&5
-$as_echo "$as_me: TCP Fast Open not enabled" >&6;}
 		;;
 esac
 
diff --git a/configure.ac b/configure.ac
index 4e345a13..3ca5f550 100755
--- a/configure.ac
+++ b/configure.ac
@@ -82,12 +82,12 @@ ACX_ARG_RPATH
 AC_ARG_ENABLE(tcp-fastopen, AC_HELP_STRING([--enable-tcp-fastopen], [Enable TCP Fast Open]))
 case "$enable_tcp_fastopen" in
 	yes)
-		# TODO: Check if it is available (linux only)
-		AC_MSG_NOTICE([TCP Fast Open enabled])
+		AC_CHECK_DECL([MSG_FASTOPEN], [], [AC_MSG_ERROR([TCP Fast Open is not available: please rerun without --enable-tcp-fastopen])], [AC_INCLUDES_DEFAULT
+#include <sys/socket.h>
+		])
 		AC_DEFINE_UNQUOTED([USE_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])
 		;;
 	no|*)
-		AC_MSG_NOTICE([TCP Fast Open not enabled])
 		;;
 esac
 
diff --git a/src/stub.c b/src/stub.c
index 3e44d961..aeb53f09 100755
--- a/src/stub.c
+++ b/src/stub.c
@@ -802,7 +802,7 @@ stub_tcp_write(int fd, getdns_tcp_state *tcp, getdns_network_req *netreq)
 		/* We have an initialized packet buffer.
 		 * Lets see how much of it we can write
 		 */
-#if defined (USE_TCP_FASTOPEN) && defined(MSG_FASTOPEN)
+#ifdef USE_TCP_FASTOPEN
 		/* We use sendto() here which will do both a connect and send */
 		written = sendto(fd, pkt, pkt_len + 2, MSG_FASTOPEN,
 					(struct sockaddr *)&(netreq->upstream->addr),
@@ -1016,7 +1016,7 @@ priv_getdns_submit_stub_request(getdns_network_req *netreq)
 			return GETDNS_RETURN_GENERIC_ERROR;
 		
 		getdns_sock_nonblock(netreq->fd);
-#if defined (USE_TCP_FASTOPEN) && defined(MSG_FASTOPEN)
+#ifdef USE_TCP_FASTOPEN
 		/* Leave the connect to the later call to sendto() */
 #else
 		if (connect(netreq->fd, (struct sockaddr *)&upstream->addr,
@@ -1047,9 +1047,10 @@ priv_getdns_submit_stub_request(getdns_network_req *netreq)
 				return GETDNS_RETURN_GENERIC_ERROR;
 			
 			getdns_sock_nonblock(upstream->fd);
-#if defined (USE_TCP_FASTOPEN) && defined(MSG_FASTOPEN)
+#ifdef USE_TCP_FASTOPEN
 		/* Leave the connect to the later call to sendto() */
 #else
+			fprintf(stderr,"connecting");
 			if (connect(upstream->fd,
 			    (struct sockaddr *)&upstream->addr,
 			    upstream->addr_len) == -1 && errno != EINPROGRESS){