diff --git a/Library/Homebrew/utils/ruby.sh b/Library/Homebrew/utils/ruby.sh
index 9a3ab2e818..b16531e9f0 100644
--- a/Library/Homebrew/utils/ruby.sh
+++ b/Library/Homebrew/utils/ruby.sh
@@ -40,7 +40,7 @@ setup-ruby-path() {
         ruby_old_version="$("$HOMEBREW_RUBY_PATH" -rrubygems -e "puts Gem::Version.new('$minimum_ruby_version') > Gem::Version.new(RUBY_VERSION)")"
       fi
 
-      if [[ "$ruby_old_version" == "true" || -n "$HOMEBREW_FORCE_VENDOR_RUBY" ]]
+      if [[ -z "$HOMEBREW_RUBY_PATH" || "$ruby_old_version" == "true" || -n "$HOMEBREW_FORCE_VENDOR_RUBY" ]]
       then
         brew vendor-install ruby
         if [[ ! -x "$vendor_ruby_path" ]]