diff --git a/layers/+lang/ess/packages.el b/layers/+lang/ess/packages.el
index 04fa13abd..71d6b5bb3 100644
--- a/layers/+lang/ess/packages.el
+++ b/layers/+lang/ess/packages.el
@@ -68,7 +68,7 @@
                  ess-nuke-trailing-whitespace-p t
                  ess-default-style 'DEFAULT)
            (when ess-disable-underscore-assign
-             (ess-toggle-underscore nil))
+             (setq ess-smart-S-assign-key nil))
 
            (define-key ess-doc-map "h" 'ess-display-help-on-object)
            (define-key ess-doc-map "p" 'ess-R-dv-pprint)