diff --git a/runtime/doc/insert.txt b/runtime/doc/insert.txt
index 31b820f..8d47a7e 100644
--- a/runtime/doc/insert.txt
+++ b/runtime/doc/insert.txt
@@ -842,6 +842,12 @@
 			Other uses include translation between two languages,
 			or grouping API functions by keyword.
 
+			If the 'thesaurusfunc' option is set, then the user
+			specified function is invoked to get the list of
+			completion matches and the 'thesaurus' option is not
+			used. See |complete-functions| for an explanation of
+			how the function is invoked and what it should return.
+
 	CTRL-T	or
 	CTRL-N		Search forward for next matching keyword.  This
 			keyword replaces the previous matching keyword.
@@ -1052,7 +1058,7 @@
 
 FUNCTIONS FOR FINDING COMPLETIONS			*complete-functions*
 
-This applies to 'completefunc' and 'omnifunc'.
+This applies to 'completefunc', 'thesaurusfunc' and 'omnifunc'.
 
 The function is called in two different ways:
 - First the function is called to find the start of the text to be completed.