diff --git a/include/libztDefs.h b/include/libztDefs.h
index 27aeee0..55c9c3a 100644
--- a/include/libztDefs.h
+++ b/include/libztDefs.h
@@ -175,7 +175,9 @@ struct sockaddr_ll {
 #define SO_STYLE                100
 #define TCP_CORK                101
 #define TCP_DEFER_ACCEPT        102
-#define TCP_KEEPIDLE            103
+#ifndef TCP_KEEPIDLE
+  #define TCP_KEEPIDLE            103
+#endif
 #define TCP_LINGER2             104
 #define TCP_QUICKACK            105
 #define TCP_SYNCNT              106