diff --git a/common.mk b/common.mk
index 80f058c3f2..d06db1c26d 100644
--- a/common.mk
+++ b/common.mk
@@ -107,7 +107,7 @@ SCRIPT_ARGS   =	--dest-dir="$(DESTDIR)" \
 		--make-flags="$(MAKEFLAGS)"
 EXTMK_ARGS    =	$(SCRIPT_ARGS) --extension $(EXTS) --extstatic $(EXTSTATIC) \
 		--make-flags="MINIRUBY='$(MINIRUBY)'" --
-INSTRUBY      =	$(MINIRUBY) $(srcdir)/tool/rbinstall.rb
+INSTRUBY      =	$(SUDO) $(MINIRUBY) $(srcdir)/tool/rbinstall.rb
 INSTRUBY_ARGS =	$(SCRIPT_ARGS) \
 		--data-mode=$(INSTALL_DATA_MODE) \
 		--prog-mode=$(INSTALL_PROG_MODE) \