diff --git a/xs/src/avrdude/ser_posix.c b/xs/src/avrdude/ser_posix.c
index beeb9bdca..af7c1fbc7 100644
--- a/xs/src/avrdude/ser_posix.c
+++ b/xs/src/avrdude/ser_posix.c
@@ -25,6 +25,7 @@
 
 #if !defined(WIN32NATIVE)
 
+#define _BSD_SOURCE    // Needed to enable various macros (such as h_addr)
 
 #include <ctype.h>
 #include <stdio.h>