diff --git a/src/node_constants.cc b/src/node_constants.cc
index 2aea278cb69..d364fb2df49 100644
--- a/src/node_constants.cc
+++ b/src/node_constants.cc
@@ -27,11 +27,14 @@
 #if !defined(_MSC_VER)
 #include <unistd.h>
 #endif
-#include <fcntl.h>
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
+// O_NONBLOCK is not exported, unless _XOPEN_SOURCE is set
+#define _XOPEN_SOURCE 500
+#include <fcntl.h>
+
 #if HAVE_OPENSSL
 # include <openssl/ssl.h>
 #endif
@@ -110,6 +113,10 @@ void DefineConstants(Handle<Object> target) {
   NODE_DEFINE_CONSTANT(target, O_DIRECT);
 #endif
 
+#ifdef O_NONBLOCK
+  NODE_DEFINE_CONSTANT(target, O_NONBLOCK);
+#endif
+
 #ifdef S_IRWXU
   NODE_DEFINE_CONSTANT(target, S_IRWXU);
 #endif