diff --git a/site/content/tutorial/04-logic/05-keyed-each-blocks/text.md b/site/content/tutorial/04-logic/05-keyed-each-blocks/text.md
index d0dec628b6..e8bac7d8df 100644
--- a/site/content/tutorial/04-logic/05-keyed-each-blocks/text.md
+++ b/site/content/tutorial/04-logic/05-keyed-each-blocks/text.md
@@ -14,4 +14,6 @@ To do that, we specify a unique identifier for the `each` block:
 {/each}
 ```
 
-The `(thing.id)` tells Svelte how to figure out what changed.
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+The `(thing.id)` tells Svelte how to figure out what changed.
+
+> You can use any object as the key, as Svelte uses a `Map` internally — in other words you could do `(thing)` instead of `(thing.id)`. Using a string or number is generally safer, however, since it means identity persists without referential equality, for example when updating with fresh data from an API server.
\ No newline at end of file