diff --git a/src/etc/emacs/rust-mode.el b/src/etc/emacs/rust-mode.el
index 4ccb18e589f..a1b8423ae3b 100644
--- a/src/etc/emacs/rust-mode.el
+++ b/src/etc/emacs/rust-mode.el
@@ -27,7 +27,7 @@
   "Amount of offset per level of indentation"
   :type 'integer
   :require 'rust-mode
-  : group 'rust-mode)
+  :group 'rust-mode)
 
 (defvar rust-syntax-table (let ((table (make-syntax-table)))
                             (c-populate-syntax-table table)