diff --git a/configure.ac b/configure.ac
index dcb02cf5..ff677984 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,6 +14,7 @@ AS_IF([test "${ac_cv_prog_cc_c99}" = "no"], [
 ])
 
 AC_SYS_LARGEFILE
+AC_DEFINE([_GNU_SOURCE], 1, [Define to include GNU extensions to POSIX])
 
 dnl Set build/host to default values
 AC_CANONICAL_HOST