diff --git a/config.mk b/config.mk
index 9bddc52..d073f56 100644
--- a/config.mk
+++ b/config.mk
@@ -10,7 +10,7 @@ LD = $(CC)
 AR = ar
 RANLIB = ranlib
 
-CPPFLAGS = -D_XOPEN_SOURCE -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
+CPPFLAGS = -D_FILE_OFFSET_BITS=64 -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
 CFLAGS   = -std=c99 -Wall -Wextra
 LDLIBS   = -lcrypt
 LDFLAGS  = -s