diff -upr drawterm-20161016.orig/Make.unix drawterm-20161016/Make.unix
--- drawterm-20161016.orig/Make.unix	2016-10-16 23:17:32.141093131 +0200
+++ drawterm-20161016/Make.unix	2016-10-16 23:17:55.724316992 +0200
@@ -6,7 +6,8 @@ AS=as
 RANLIB=ranlib
 X11=/usr/X11R6
 CC=gcc
-CFLAGS=-Wall -Wno-missing-braces -ggdb -I$(ROOT) -I$(ROOT)/include -I$(ROOT)/kern -c -I$(X11)/include -D_THREAD_SAFE $(PTHREAD) -O2
+CFLAGS?=-O2
+CFLAGS+=-Wall -Wno-missing-braces -ggdb -I$(ROOT) -I$(ROOT)/include -I$(ROOT)/kern -c -I$(X11)/include -D_THREAD_SAFE $(PTHREAD)
 O=o
 OS=posix
 GUI=x11