diff --git a/luaa.c b/luaa.c
index c287d1a2e..6a83ec062 100644
--- a/luaa.c
+++ b/luaa.c
@@ -1219,6 +1219,11 @@ luaA_cs_init(void)
 
     addr = socket_getaddr(getenv("DISPLAY"));
 
+/* Needed for some OSes like Solaris */
+#ifndef SUN_LEN
+#define SUN_LEN(ptr) ((size_t) (((struct sockaddr_un *) 0)->sun_path) + strlen ((ptr)->sun_path))
+#endif
+
     if(bind(csfd, (const struct sockaddr *) addr, SUN_LEN(addr)))
     {
         if(errno == EADDRINUSE)