diff --git a/Makefile b/Makefile
index 6fbae02..59da4ed 100644
--- a/Makefile
+++ b/Makefile
@@ -1,12 +1,15 @@
+MANDIR=/usr/share/man
+SBINDIR=/usr/sbin
+
 all:
 	chmod 755 make-ca.sh help2man
 	./help2man -N ./make-ca.sh -o make-ca.sh.1
 
 install:
-	/usr/bin/install -vdm755 $(DESTDIR)/usr/sbin
-	/usr/bin/install -vdm755 $(DESTDIR)/usr/share/man/man1
-	install -vm755 make-ca.sh $(DESTDIR)/usr/sbin
-	install -vm644 make-ca.sh.1 $(DESTDIR)/usr/share/man/man1
+	/usr/bin/install -vdm755 $(DESTDIR)$(SBINDIR)
+	/usr/bin/install -vdm755 $(DESTDIR)$(MANDIR)/man1
+	install -vm755 make-ca.sh $(DESTDIR)$(SBINDIR)
+	install -vm644 make-ca.sh.1 $(DESTDIR)$(MANDIR)/man1
 
 .PHONY: all install