Index: uspace/lib/c/Makefile
===================================================================
--- uspace/lib/c/Makefile	(revision 1edd6d0c4201fd549dcce1ac7154c0ee7d6ab4c9)
+++ uspace/lib/c/Makefile	(revision 26f5bdf7b49e5a516031722f25a06c6f2346c254)
@@ -34,5 +34,5 @@
 
 EXTRA_OUTPUT = $(START_FILES)
-EXTRA_CFLAGS += -fno-builtin
+EXTRA_CFLAGS += -fno-builtin -D_LIBC_SOURCE
 LIBRARY = libc
 SOVERSION = 0.0