diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 7246ff8..220a19b 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -548,6 +548,12 @@
 like in JavaScript: >
 	var dict = {["key" .. nr]: value}
 
+The key type can be string, number, bool or float.  Other types result in an
+error.  A number can be given with and without the []: >
+	var dict = {123: 'without', [456]: 'with'}
+	echo dict
+	{'456': 'with', '123': 'without'}
+
 
 No :xit, :t, :append, :change or :insert ~