diff --git a/configure.ac b/configure.ac
index 83a06ed..0ad9603 100644
--- a/configure.ac
+++ b/configure.ac
@@ -34,6 +34,7 @@ AC_HEADER_STDC
 AC_HEADER_STDBOOL
 AC_CHECK_HEADERS([stdio.h stdlib.h stdint.h stddef.h stdbool.h])
 AC_CHECK_FUNCS(strdup, [AC_DEFINE([_XOPEN_SOURCE], [600], [Enable POSIX extensions if present])])
+AC_DEFINE(_NETBSD_SOURCE, 1, [Define on NetBSD to activate all library features])
 
 # Checks for types
 AC_TYPE_SIZE_T