diff --git a/Makefile b/Makefile
index 1bdc7d6..4afd717 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@
 include config.mk
 
 # flags for compiling
-DWLCPPFLAGS = -I. -DWLR_USE_UNSTABLE -DVERSION=\"$(VERSION)\"
+DWLCPPFLAGS = -I. -DWLR_USE_UNSTABLE -D_POSIX_C_SOURCE=200809L -DVERSION=\"$(VERSION)\"
 
 # Wayland utils
 WAYLAND_PROTOCOLS = `pkg-config --variable=pkgdatadir wayland-protocols`
diff --git a/dwl.c b/dwl.c
index 58dc4db..530ee4e 100644
--- a/dwl.c
+++ b/dwl.c
@@ -1,7 +1,6 @@
 /*
  * See LICENSE file for copyright and license details.
  */
-#define _POSIX_C_SOURCE 200809L
 #include <getopt.h>
 #include <libinput.h>
 #include <limits.h>