diff --git a/configure.ac b/configure.ac
index 1159f2bc..46dac344 100644
--- a/configure.ac
+++ b/configure.ac
@@ -160,30 +160,21 @@ case "$enable_debug_sec" in
 		;;
 esac
 
-# AC_ARG_ENABLE(tcp-fastopen, AC_HELP_STRING([--enable-tcp-fastopen], [Enable TCP Fast Open]))
-# case "$enable_tcp_fastopen" in
-#   yes)
-#       AC_CHECK_DECL([CONNECT_RESUME_ON_READ_WRITE], [], [AC_MSG_ERROR([TCP Fast Open is not available: please rerun without --enable-tcp-fastopen])], [AC_INCLUDES_DEFAULT
-# #include <sys/socket.h>
-#       ])
-#       AC_DEFINE_UNQUOTED([USE_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])
-#       ;;
-#   no|*)
-#       ;;
-# esac
-
 AC_ARG_ENABLE(tcp-fastopen, AC_HELP_STRING([--disable-tcp-fastopen], Disable TCP Fast Open (default=enabled if available)),
     enable_tcp_fastopen="$enableval", enable_tcp_fastopen=yes)
 if test "x$enable_tcp_fastopen" = xno; then
         AC_MSG_WARN([TCP Fast Open is disabled])
 else
-        my_have_linux_tfo=1
-        AC_CHECK_DECL([MSG_FASTOPEN], [AC_DEFINE_UNQUOTED([USE_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])],
-                      my_have_linux_tfo=0, [#include <sys/socket.h>])
-        if test my_have_linux_tfo=0; then
-            AC_CHECK_DECL([CONNECT_RESUME_ON_READ_WRITE], [AC_DEFINE_UNQUOTED([USE_OSX_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])],
-                        [AC_MSG_WARN([TCP Fast Open is not available, continuing without])], [#include <sys/socket.h>])
-        fi
+    case `uname` in
+        Linux) AC_CHECK_DECL([MSG_FASTOPEN], [AC_DEFINE_UNQUOTED([USE_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])],
+                          [AC_MSG_WARN([TCP Fast Open is not available, continuing without])], [#include <sys/socket.h>])
+          ;;
+        Darwin) AC_CHECK_DECL([CONNECT_RESUME_ON_READ_WRITE], [AC_DEFINE_UNQUOTED([USE_OSX_TCP_FASTOPEN], [1], [Define this to enable TCP fast open.])],
+                      [AC_MSG_WARN([TCP Fast Open is not available, continuing without])], [#include <sys/socket.h>])
+          ;;
+        *) AC_MSG_WARN([TCP Fast Open is not available, continuing without])
+          ;;
+    esac
 fi
 
 AC_ARG_ENABLE(native-stub-dnssec, AC_HELP_STRING([--disable-native-stub-dnssec], [Disable native stub DNSSEC support]))