diff --git a/Makefile b/Makefile
index 4ae8d889c5f1bd35c5fc915426e008418507d881..9e3d5a22c5710325afb465891dbbb6a1f69937b3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-PREFIX=/usr
+PREFIX?=/usr
 DOCDIR_PREFIX=$(PREFIX)/share/doc
 DOCDIR=$(DOCDIR_PREFIX)/$(self)
 ZSHDIR=$(PREFIX)/share/zsh/vendor-completions