diff --git a/src/luasocket.h b/src/luasocket.h
index f75d21f..0121a15 100644
--- a/src/luasocket.h
+++ b/src/luasocket.h
@@ -18,7 +18,19 @@
 * This macro prefixes all exported API functions
 \*-------------------------------------------------------------------------*/
 #ifndef LUASOCKET_API
-#define LUASOCKET_API extern
+#ifdef _WIN32
+#define LUASOCKET_API __declspec(dllexport)
+#else
+#define LUASOCKET_API __attribute__ ((visibility ("default")))
+#endif
+#endif
+
+#ifndef LUASOCKET_PRIVATE
+#ifdef _WIN32
+#define LUASOCKET_PRIVATE
+#else
+#define LUASOCKET_PRIVATE __attribute__ ((visibility ("hidden")))
+#endif
 #endif
 
 /*-------------------------------------------------------------------------*\