--- Makefile.orig	2013-07-22 16:11:22.000000000 +0200
+++ Makefile	2013-10-03 21:24:28.000000000 +0200
@@ -40,7 +40,7 @@
 $(error "Platform '$(SYSTEM)' not supported")
 endif
 
-GLEW_DEST ?= /usr
+GLEW_DEST ?= $(PREFIX)
 BINDIR    ?= $(GLEW_DEST)/bin
 LIBDIR    ?= $(GLEW_DEST)/lib
 INCDIR    ?= $(GLEW_DEST)/include/GL
@@ -71,7 +71,7 @@
 OPT = $(POPT)
 endif
 INCLUDE = -Iinclude
-CFLAGS = $(OPT) $(WARN) $(INCLUDE) $(CFLAGS.EXTRA)
+CFLAGS += $(OPT) $(WARN) $(INCLUDE) $(CFLAGS.EXTRA)
 
 all debug: glew.lib glew.lib.mx glew.bin
 
