diff --git a/config.mk b/config.mk
index 9753614..f340f0c 100644
--- a/config.mk
+++ b/config.mk
@@ -6,6 +6,6 @@ VERSION = 0.0
 
 AR = ar
 
-CPPFLAGS = -D_BSD_SOURCE -D_POSIX_C_SOURCE=2
+CPPFLAGS = -D_POSIX_C_SOURCE=200112L
 CFLAGS   = -Os -ansi -Wall -pedantic $(CPPFLAGS)
 LDFLAGS  = -s -static