diff --git a/zsh/ruby.zsh b/zsh/ruby.zsh
index 39ba784..5cce0e4 100755
--- a/zsh/ruby.zsh
+++ b/zsh/ruby.zsh
@@ -79,6 +79,7 @@ install_ruby_global_packages() {
     seeing_is_believing
     solargraph
     steep
+    syntax_tree
     yard
   )