diff --git a/runtime/doc/insert.txt b/runtime/doc/insert.txt
index 1c25276c6f..c478428d5a 100644
--- a/runtime/doc/insert.txt
+++ b/runtime/doc/insert.txt
@@ -639,6 +639,9 @@ and one of the CTRL-X commands.  You exit CTRL-X mode by typing a key that is
 not a valid CTRL-X mode command.  Valid keys are the CTRL-X command itself,
 CTRL-N (next), and CTRL-P (previous).
 
+By default, the possible completions are showed in a menu and the first
+completion is inserted into the text. This can be adjusted with 'completeopt'.
+
 To get the current completion information, |complete_info()| can be used.
 Also see the 'infercase' option if you want to adjust the case of the match.
 
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 0defec9956..e76e23e8a8 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1651,6 +1651,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 		    completion in the preview window.  Only works in
 		    combination with "menu" or "menuone".
 
+	This option does not apply to |cmdline-completion|. See 'wildoptions'
+	for that.
+
 						*'completeslash'* *'csl'*
 'completeslash' 'csl'	string	(default "")
 			local to buffer
@@ -7232,6 +7235,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 				d	#define
 				f	function
 
+	This option does not apply to |ins-completion|. See 'completeopt' for
+	that.
+
 						*'winaltkeys'* *'wak'*
 'winaltkeys' 'wak'	string	(default "menu")
 			global
diff --git a/runtime/lua/vim/_meta/options.lua b/runtime/lua/vim/_meta/options.lua
index 2195ebd1ca..62ecba8353 100644
--- a/runtime/lua/vim/_meta/options.lua
+++ b/runtime/lua/vim/_meta/options.lua
@@ -1184,6 +1184,9 @@ vim.go.cia = vim.go.completeitemalign
 --- 	    completion in the preview window.  Only works in
 --- 	    combination with "menu" or "menuone".
 ---
+--- This option does not apply to `cmdline-completion`. See 'wildoptions'
+--- for that.
+---
 --- @type string
 vim.o.completeopt = "menu,popup"
 vim.o.cot = vim.o.completeopt
@@ -7925,6 +7928,9 @@ vim.go.wim = vim.go.wildmode
 --- 			d	#define
 --- 			f	function
 ---
+--- This option does not apply to `ins-completion`. See 'completeopt' for
+--- that.
+---
 --- @type string
 vim.o.wildoptions = "pum,tagfile"
 vim.o.wop = vim.o.wildoptions
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index da13075529..f5a3eb493b 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -1640,6 +1640,9 @@ local options = {
            preview  Show extra information about the currently selected
         	    completion in the preview window.  Only works in
         	    combination with "menu" or "menuone".
+
+        This option does not apply to |cmdline-completion|. See 'wildoptions'
+        for that.
       ]=],
       full_name = 'completeopt',
       list = 'onecomma',
@@ -10290,6 +10293,9 @@ local options = {
         		is displayed per line.  Often used tag kinds are:
         			d	#define
         			f	function
+
+        This option does not apply to |ins-completion|. See 'completeopt' for
+        that.
       ]=],
       full_name = 'wildoptions',
       list = 'onecomma',