diff --git a/config.mk b/config.mk
index f8128b3..5c62469 100644
--- a/config.mk
+++ b/config.mk
@@ -14,6 +14,6 @@ LDFLAGS  = -g
 
 #CC = tcc
 #LD = $(CC)
-#CPPFLAGS = -D_POSIX_C_SOURCE=200112L
+#CPPFLAGS = -D_BSD_SOURCE -D_GNU_SOURCE
 #CFLAGS   = -Os -Wall $(CPPFLAGS)
 #LDFLAGS  =