diff --git a/mode-customizations/ruby-mode.el b/mode-customizations/ruby-mode.el
index b823640..dbff83f 100644
--- a/mode-customizations/ruby-mode.el
+++ b/mode-customizations/ruby-mode.el
@@ -8,6 +8,7 @@
 (add-to-list 'auto-mode-alist '("\\.rake\\'" . ruby-mode))
 (add-to-list 'auto-mode-alist '("\\.gemspec\\'" . ruby-mode))
 (add-to-list 'auto-mode-alist '("\\.rabl\\'" . ruby-mode))
+(add-to-list 'auto-mode-alist '("\\.prawn\\'" . ruby-mode))
 
 (add-hook 'ruby-mode-hook
           (lambda ()