diff --git a/pyconfig.h.in b/pyconfig.h.in
index 93ef151..705976d 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -817,6 +817,9 @@
 /* Define to 1 if on MINIX. */
 #undef _MINIX
 
+/* Define on NetBSD to activate all library features */
+#undef _NETBSD_SOURCE
+
 /* Define _OSF_SOURCE to get the makedev macro. */
 #undef _OSF_SOURCE