diff --git a/Makefile b/Makefile
index f5c9854..8bf93ab 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
-PREFIX = /usr/local
-MANDIR = ${PREFIX}/share/man
+PREFIX ?= /usr/local
+MANDIR ?= ${PREFIX}/share/man
 
 CFLAGS += -I${PREFIX}/include
 LDFLAGS += -L${PREFIX}/lib