--- Makefile.orig
+++ Makefile
@@ -81,6 +81,7 @@
 
 OPAMINSTALLER_FLAGS = --prefix "$(DESTDIR)$(prefix)"
 OPAMINSTALLER_FLAGS += --mandir "$(DESTDIR)$(mandir)"
+OPAMINSTALLER_FLAGS += --docdir "$(DESTDIR)$(prefix)/share/doc"
 
 # With ocamlfind, prefer to install to the standard directory rather
 # than $(prefix) if there are no overrides