diff --git a/config.mk b/config.mk
index 7db6cba..be145d2 100644
--- a/config.mk
+++ b/config.mk
@@ -60,7 +60,7 @@ INCS = -I${X11INC} -I${FREETYPEINC} ${YAJLINC} ${PANGOINC} ${BDINC}
 LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS}  ${XRENDER} ${MPDCLIENT} ${XEXTLIB} ${XCBLIBS} ${KVMLIB} ${PANGOLIB} ${YAJLLIBS} ${IMLIB2LIBS} $(BDLIBS)
 
 # flags
-CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D__XSI_VISIBLE=1 -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
 #CFLAGS   = -g -std=c99 -pedantic -Wall -O0 ${INCS} ${CPPFLAGS}
 CFLAGS   = -std=c99 -pedantic -Wall -Wno-unused-function -Wno-deprecated-declarations -Os ${INCS} ${CPPFLAGS}
 LDFLAGS  = ${LIBS}