1 files changed, 1 insertions, 1 deletions

diff --git a/config.mk b/config.mk
index 2a8a719..91ebfd6 100644
--- a/config.mk
+++ b/config.mk
@@ -1,6 +1,6 @@
 PREFIX = /usr/local
 
-CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700L
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700L -D_POSIX_C_SOURCE=200809L
 CFLAGS = -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os
 LDFLAGS = -lm -lX11