diff --git a/Library/Homebrew/utils/ruby.sh b/Library/Homebrew/utils/ruby.sh
index bbd42a643c..3293949f53 100644
--- a/Library/Homebrew/utils/ruby.sh
+++ b/Library/Homebrew/utils/ruby.sh
@@ -17,7 +17,7 @@ test_ruby() {
 # HOMEBREW_PATH is set by global.rb
 # shellcheck disable=SC2154
 find_ruby() {
-  if [[ -n "${HOMEBREW_MACOS}" && -n "${HOMEBREW_USE_RUBY_FROM_PATH}" ]]
+  if [[ -n "${HOMEBREW_MACOS}" && -z "${HOMEBREW_USE_RUBY_FROM_PATH}" ]]
   then
     echo "/System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby"
   else