1 diff --git a/configure.ac b/configure.ac
2 index 466f7f9..0dec17f 100644
5 @@ -27,7 +27,7 @@ AM_INIT_AUTOMAKE([foreign dist-bzip2 no-dist-gzip])
6 AC_CONFIG_HEADERS(config.h)
9 -SET_FEATURES="-D_ISOC99_SOURCE -D_POSIX_C_SOURCE=200112L"
10 +SET_FEATURES="-D_ISOC99_SOURCE -D_POSIX_C_SOURCE=200112L -D_XOPEN_SOURCE=500"