diff --git a/config.project b/config.project
index c475cb3..180cb49 100644
--- a/config.project
+++ b/config.project
@@ -28,7 +28,8 @@ mb_default_shell=sh
 
 # switches
 mb_default_cflags_debug=
-mb_default_cflags_common="-std=c99 -D_XOPEN_SOURCE=700 -I\$(PROJECT_DIR)/src/internal -I\$(PROJECT_DIR)/include -Ibuild"
+mb_default_cflags_common="-std=c99 -D_XOPEN_SOURCE=700 -D_GNU_SOURCE"
+mb_default_cflags_common="$mb_default_cflags_common -I\$(PROJECT_DIR)/src/internal -I\$(PROJECT_DIR)/include -Ibuild"
 mb_default_cflags_cmdline=
 mb_default_cflags_config=
 mb_default_cflags_sysroot=