--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .POSIX:
 .SUFFIXES:
 
-CXX = c++
+CXX ?= c++
 
 debug = no
 static = no
@@ -33,7 +33,7 @@
 version = $(shell cat .version 2>/dev/null || git describe --tags HEAD 2>/dev/null | sed s/^v// || echo unknown)
 version != cat .version 2>/dev/null || ( git describe --tags HEAD 2>/dev/null | sed s/^v// ) || echo unknown
 
-PREFIX = /usr/local
+PREFIX ?= /usr/local
 DESTDIR = # root dir
 
 bindir = $(DESTDIR)$(PREFIX)/bin