diff --git a/features.txt b/features.txt
index 841917b83c..47f3388511 100644
--- a/features.txt
+++ b/features.txt
@@ -280,6 +280,10 @@ decorators
 # https://github.com/tc39/proposal-duplicate-named-capturing-groups
 regexp-duplicate-named-groups
 
+# Symbols as WeakMap keys
+# https://github.com/tc39/proposal-symbols-as-weakmap-keys
+symbols-as-weakmap-keys
+
 ## Standard language features
 #
 # Language features that have been included in a published version of the