1 files changed, 1 insertions, 1 deletions
diff --git a/config.mk b/config.mk
index 95690f9..7b08bf1 100644
--- a/config.mk
+++ b/config.mk
@@ -23,7 +23,7 @@ INCS = -I${X11INC} -I${FREETYPEINC}
 LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS}
 
 # flags
-CPPFLAGS = -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
+CPPFLAGS = -D_BSD_SOURCE -D_XOPEN_SOURCE=500 -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
 CFLAGS   = -ansi -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
 LDFLAGS  = -s ${LIBS}