diff --git a/modules/prelude-ruby.el b/modules/prelude-ruby.el
index 2b0bff3..0f8a085 100644
--- a/modules/prelude-ruby.el
+++ b/modules/prelude-ruby.el
@@ -46,6 +46,7 @@
 (add-to-list 'auto-mode-alist '("\\.thor\\'" . ruby-mode))
 (add-to-list 'auto-mode-alist '("Thorfile\\'" . ruby-mode))
 (add-to-list 'auto-mode-alist '("Vagrantfile\\'" . ruby-mode))
+(add-to-list 'auto-mode-alist '("\\.jbuilder\\'" . ruby-mode))
 
 ;; We never want to edit Rubinius bytecode
 (add-to-list 'completion-ignored-extensions ".rbc")