commit https://github.com/vim/vim/commit/888ccac8902cee186fbd47e971881f6d9b19c068 Author: Bram Moolenaar <Bram@vim.org> Date: Sat Jun 4 18:49:36 2016 +0200 patch 7.4.1895 Problem: Cannot use a window ID where a window number is expected. Solution: Add LOWEST_WIN_ID, so that the window ID can be used where a number is expected.

--- a/src/vim.h
+++ b/src/vim.h
@@ -2334,4 +2334,7 @@ int vim_main2(int argc, char **argv);
 #define DIP_OPT	    0x10	/* also use "opt" directory in 'packpath' */
 #define DIP_NORTP   0x20	/* do not use 'runtimepath' */
 
+/* Lowest number used for window ID. Cannot have this many windows. */
+#define LOWEST_WIN_ID 1000
+
 #endif /* VIM__H */