diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 79c5409..bd05691 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -2554,6 +2554,7 @@
 popup_filter_yesno({id}, {key}) Number	filter for a dialog popup window
 popup_getoptions({id})		Dict	get options of popup window {id}
 popup_getpos({id})		Dict	get position of popup window {id}
+popup_getpreview()		Number	get window ID of preview popup window
 popup_hide({id})		none	hide popup menu {id}
 popup_menu({what}, {options})	Number	create a popup window used as a menu
 popup_move({id}, {options})	none	set position of popup window {id}
diff --git a/runtime/doc/popup.txt b/runtime/doc/popup.txt
index 52d0892..d696e28 100644
--- a/runtime/doc/popup.txt
+++ b/runtime/doc/popup.txt
@@ -1,4 +1,4 @@
-*popup.txt*  For Vim version 8.1.  Last change: 2019 Jul 18
+*popup.txt*  For Vim version 8.1.  Last change: 2019 Jul 28
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -335,6 +335,10 @@
 
 		If popup window {id} is not found an empty Dict is returned.
 
+popup_getpreview()					*popup_getpreview()*
+		Get the |window-ID| for the popup preview window.
+		Return zero if there is none.
+
 
 popup_hide({id})						*popup_hide()*
 		If {id} is a displayed popup, hide it now. If the popup has a