Index: uspace/lib/posix/Makefile
===================================================================
--- uspace/lib/posix/Makefile	(revision b501de784dd26902c687e3142fa124f7aecd3384)
+++ uspace/lib/posix/Makefile	(revision 31a566bc2fcd89f3a4bb7a0ed41cb3798eacac42)
@@ -31,5 +31,5 @@
 LIBRARY = libposix
 
-EXTRA_CFLAGS = -Iinclude/posix
+EXTRA_CFLAGS = -Iinclude/posix -D_XOPEN_SOURCE
 
 EXPORT_FILES = \