diff --git a/runtime/doc/gui.txt b/runtime/doc/gui.txt
index decc7bf..38adf77 100644
--- a/runtime/doc/gui.txt
+++ b/runtime/doc/gui.txt
@@ -155,8 +155,8 @@
 window Vim is running in with these commands: >
 	:!xwininfo -id $WINDOWID
 	:!xprop -id $WINDOWID
-	:execute '!xwininfo -id ' . v:windowid
-	:execute '!xprop -id ' . v:windowid
+	:execute '!xwininfo -id ' .. v:windowid
+	:execute '!xprop -id ' .. v:windowid
 <
 							*gui-IME* *iBus*
 Input methods for international characters in X that rely on the XIM