diff --git a/docs/usage.md b/docs/usage.md
index 0500f8538..d4c82e4e6 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -445,6 +445,7 @@ The following custom field types are supported:
 - `Number`: float number e.g. 12.3456
 - `Monetary`: [ISO 4217 currency code](https://en.wikipedia.org/wiki/ISO_4217#List_of_ISO_4217_currency_codes) and a number with exactly two decimals, e.g. USD12.30
 - `Document Link`: reference(s) to other document(s) displayed as links, automatically creates a symmetrical link in reverse
+- `Select`: a pre-defined list of strings from which the user can choose
 
 ## Share Links