--- sauerbraten/src/Makefile
+++ sauerbraten/src/Makefile
@@ -1,6 +1,8 @@
-CXXOPTFLAGS= -O3 -fomit-frame-pointer
-INCLUDES= -Ishared -Iengine -Ifpsgame -Irpggame -Ienet/include -I/usr/X11R6/include `sdl-config --cflags`
-CXXFLAGS= -w -fsigned-char $(CXXOPTFLAGS) $(INCLUDES)
+ifeq ($(origin CXXFLAGS), default)
+	CXXFLAGS := -O3 -fomit-frame-pointer
+endif
+INCLUDES := -Ishared -Iengine -Ifpsgame -Irpggame -Ienet/include -I/usr/X11R6/include `sdl-config --cflags`
+CXXFLAGS := $(CXXFLAGS) -w -fsigned-char $(INCLUDES)
 
 PLATFORM_PREFIX=native