diff --git a/Makefile b/Makefile
index 429ecd6e589ea37cad8cf40716767c088e374347..ebe4b2b6cf2e67b2d7c4b1084f6556b545670880 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 PREFIX=/usr
-DOCDIR=$(PREFIX)/share/doc/$(self)
+DOCDIR_PREFIX=$(PREFIX)/share/doc
+DOCDIR=$(DOCDIR_PREFIX)/$(self)
 ZSHDIR=$(PREFIX)/share/zsh/vendor-completions
 RONN ?= ronn
 
@@ -39,7 +40,7 @@ uninstall:
 purge: uninstall
 	rmdir -p --ignore-fail-on-non-empty $(DESTDIR)$(PREFIX)/bin/
 	rmdir -p --ignore-fail-on-non-empty $(DESTDIR)$(PREFIX)/share/man/man1/
-	rmdir -p --ignore-fail-on-non-empty $(DESTDIR)$(shell dirname $(DOCDIR))
+	rmdir -p --ignore-fail-on-non-empty $(DESTDIR)$(DOCDIR_PREFIX)
 	rmdir -p --ignore-fail-on-non-empty $(DESTDIR)$(ZSHDIR)
 
 test: