@@ -1331,11 +1331,11 @@
 	AC_CHECK_HEADERS([arpa/inet.h netdb.h])
 	AC_CHECK_HEADER(netipx/ipx.h, [
 		AC_DEFINE(OF_HAVE_NETIPX_IPX_H, 1,
 			[Whether we have netipx/ipx.h])
 	])
-	AC_CHECK_HEADERS(sys/un.h, [
+	AC_CHECK_HEADER(sys/un.h, [
 		AC_DEFINE(OF_HAVE_SYS_UN_H, 1, [Whether we have sys/un.h])
 	])
 
 	AC_CHECK_MEMBER([struct sockaddr_in6.sin6_addr], [
 		AC_EGREP_CPP(egrep_cpp_yes, [
@@ -1533,10 +1533,24 @@
 			AC_SUBST(OF_SELECT_KERNEL_EVENT_OBSERVER_M,
 				"OFSelectKernelEventObserver.m")
 		])
 		;;
 	esac
+
+	AC_CHECK_HEADERS(Security/SecureTransport.h, [
+		old_LIBS="$LIBS"
+		LIBS="-framework Security -framework Foundation $LIBS"
+
+		AC_CHECK_FUNC(SSLHandshake, [
+			AC_DEFINE(HAVE_SECURE_TRANSPORT, 1,
+				[Whether we have Secure Transport])
+			AC_SUBST(OF_SECURE_TRANSPORT_TLS_STREAM_M,
+				"OFSecureTransportTLSStream.m")
+		], [
+			LIBS="$old_LIBS"
+		])
+	])
 
 	AS_IF([test x"$enable_threads" != x"no"], [
 		AC_SUBST(OF_HTTP_CLIENT_TESTS_M, "OFHTTPClientTests.m")
 	])