--- a/sipp.hpp
+++ b/sipp.hpp
@@ -605,7 +605,7 @@
 #define WS_BUFFER 2 /* Buffer the message if there is no room for writing the message. */
 
 
-#if defined (__hpux) || defined (__alpha) && !defined (__FreeBSD__)
+#if defined (__hpux) || defined (__digital__) && defined(__unix__)
 #define sipp_socklen_t  int
 #else
 #define sipp_socklen_t  socklen_t