diff -p -up ratpoints-2.1.2/Makefile.orig ratpoints-2.1.2/Makefile
--- ratpoints-2.1.2/Makefile.orig	2009-07-15 14:29:13.000000000 -0300
+++ ratpoints-2.1.2/Makefile	2009-07-15 14:33:05.000000000 -0300
@@ -27,7 +27,10 @@ CC = gcc
 RM = rm -f
 INSTALL = cp
 
-INSTALL_DIR = /usr/local
+PREFIX = /usr
+BINDIR = $(PREFIX)/bin
+LIBDIR = $(PREFIX)/lib
+INCDIR = $(PREFIX)/include
 
 CCFLAGS1 = -Wall -O2 -fomit-frame-pointer -DRATPOINTS_MAX_BITS_IN_PRIME=${PRIME_SIZE} -DUSE_SSE
 # for gcc on Apple, may have to add '-fnested-functions' to CCFLAGS1
@@ -56,14 +59,14 @@ test: rptest testbase
 	diff -q testbase rptest.out
 
 install-bin: ratpoints
-	${INSTALL} ratpoints ${INSTALL_DIR}/bin/
-	chmod 755 ${INSTALL_DIR}/bin/ratpoints
+	${INSTALL} ratpoints ${DESTDIR}${BINDIR}
+	chmod 755 ${DESTDIR}${BINDIR}/ratpoints
 
 install-lib: ratpoints.h libratpoints.a
-	${INSTALL} ratpoints.h ${INSTALL_DIR}/include/
-	chmod 644 ${INSTALL_DIR}/include/ratpoints.h
-	${INSTALL} libratpoints.a ${INSTALL_DIR}/lib/
-	chmod 644 ${INSTALL_DIR}/lib/libratpoints.a
+	${INSTALL} ratpoints.h ${DESTDIR}${INCDIR}
+	chmod 644 ${DESTDIR}${INCDIR}/ratpoints.h
+	${INSTALL} libratpoints.a ${DESTDIR}${LIBDIR}
+	chmod 644 ${DESTDIR}${LIBDIR}/libratpoints.a
 
 install: install-bin install-lib