diff --git a/website/docs/api/stringstore.mdx b/website/docs/api/stringstore.mdx
index 7e380f5f8..cb1118ff0 100644
--- a/website/docs/api/stringstore.mdx
+++ b/website/docs/api/stringstore.mdx
@@ -8,6 +8,13 @@ Look up strings by 64-bit hashes. As of v2.0, spaCy uses hash values instead of
 integer IDs. This ensures that strings always map to the same ID, even from
 different `StringStores`.
 
+<Infobox variant="warning">
+
+Please note that the `StringStore` size is not static and increases as texts are
+processed and new tokens are seen.
+
+</Infobox>
+
 ## StringStore.\_\_init\_\_ {id="init",tag="method"}
 
 Create the `StringStore`.
diff --git a/website/docs/api/vocab.mdx b/website/docs/api/vocab.mdx
index 3faf1f1a0..625841823 100644
--- a/website/docs/api/vocab.mdx
+++ b/website/docs/api/vocab.mdx
@@ -10,6 +10,13 @@ The `Vocab` object provides a lookup table that allows you to access
 [`StringStore`](/api/stringstore). It also owns underlying C-data that is shared
 between `Doc` objects.
 
+<Infobox variant="warning">
+
+Please note that the `Vocab` size is not static and increases as texts are
+processed and new tokens are seen.
+
+</Infobox>
+
 ## Vocab.\_\_init\_\_ {id="init",tag="method"}
 
 Create the vocabulary.