diff --git a/docs/api.md b/docs/api.md
index cd3e462da..40b597ad8 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -192,8 +192,8 @@ The endpoint supports the following optional form fields:
 -   `tags`: Similar to correspondent. Specify this multiple times to
     have multiple tags added to the document.
 -   `archive_serial_number`: An optional archive serial number to set.
--   `custom_fields`: An array of custom field ids to assign (with an empty
-    value) to the document.
+-   `custom_fields`: Either n array of custom field ids to assign (with an empty
+    value) to the document or an object mapping field id -> value.
 
 The endpoint will immediately return HTTP 200 if the document consumption
 process was started successfully, with the UUID of the consumption task