diff --git a/config.mk b/config.mk
index a3ffc4d..078cf5e 100644
--- a/config.mk
+++ b/config.mk
@@ -15,5 +15,5 @@ LDFLAGS  = -g
 #CC = tcc
 #LD = $(CC)
 #CPPFLAGS = -D_POSIX_C_SOURCE=200112L
-#CFLAGS   = -Os -Wall $(CPPFLAGS)
+#CFLAGS   = -Os -Wall $(CPPFLAGS) -D_GNU_SOURCE
 #LDFLAGS  =