diff --git a/lisp/textmodes/css-mode.el b/lisp/textmodes/css-mode.el
index 6ce7172063c..246a3144a1b 100644
--- a/lisp/textmodes/css-mode.el
+++ b/lisp/textmodes/css-mode.el
@@ -327,8 +327,8 @@
     ("place-self" justify-self align-self)
     ("row-gap" "normal" length-percentage)
 
-    ;; CSS Flexible Box Layout Module Level 2
-    ;; (https://www.w3.org/TR/css-flexbox-2/#property-index)
+    ;; CSS Flexible Box Layout Module Level 1
+    ;; (https://www.w3.org/TR/css-flexbox-1/#property-index)
     ("flex" "none" flex-grow flex-shrink flex-basis)
     ("flex-basis" "auto" "content" width)
     ("flex-direction" "row" "row-reverse" "column" "column-reverse")