diff --git a/doc/outline.txt b/doc/outline.txt
index 8be7c8c..b611e0f 100644
--- a/doc/outline.txt
+++ b/doc/outline.txt
@@ -483,7 +483,7 @@ External providers from plugins should define the provider module at
     The function should return a list of "symbol tables".
     Each symbol table should have these fields:
     - name: string – displayed in the outline
-    - kind: integer – determines the icon to use
+    - kind: integer|string – determines the icon to use
     - selectionRange: table with fields `start` and `end`, each have fields
         `line` and `character`, each integers:
         `{ start = { line = ?, character = ? }, ['end'] = { line = ?, character = ? } }`