-CPPFLAGS = -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
-CFLAGS = -ansi -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
-LDFLAGS = -s ${LIBS}
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_POSIX_C_SOURCE=200809L -DVERSION=\"$(VERSION)\" $(XINERAMAFLAGS)
+CFLAGS = -std=c99 -pedantic -Wall -Os $(INCS) $(CPPFLAGS)
+LDFLAGS = $(LIBS)