diff --git a/dtrace-script-mode.el b/dtrace-script-mode.el
index b3fd2f3..409bf37 100644
--- a/dtrace-script-mode.el
+++ b/dtrace-script-mode.el
@@ -352,6 +352,8 @@ With argument, repeat that many times; negative args move backward."
   (push-mark (point))
   (dtrace-script-mode-beginning-of-function))
 
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.d\\'" . dtrace-script-mode))
 
 ;;;###autoload
 (define-derived-mode dtrace-script-mode c-mode "DTrace"