commit https://github.com/vim/vim/commit/35a4cfa200917dd171b1fff3cd5b6cee9add673d Author: Bram Moolenaar <Bram@vim.org> Date: Sun Aug 14 16:07:48 2016 +0200 patch 7.4.2209 Problem: Cannot map <M-">. (Stephen Riehm) Solution: Solve the memory access problem in another way. (Dominique Pelle) Allow for using <M-\"> in a string.

--- a/src/option.c
+++ b/src/option.c
@@ -9478,7 +9478,7 @@ find_key_option(char_u *arg)
     {
 	--arg;			    /* put arg at the '<' */
 	modifiers = 0;
-	key = find_special_key(&arg, &modifiers, TRUE, TRUE);
+	key = find_special_key(&arg, &modifiers, TRUE, TRUE, FALSE);
 	if (modifiers)		    /* can't handle modifiers here */
 	    key = 0;
     }