diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 939a81d..9b15c58 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -150,6 +150,18 @@
 (the ^[ is a real <Esc> here, use CTRL-V <Esc> to enter it)
 The advantage over a mapping is that it works in all situations.
 
+You can define any key codes, e.g.: >
+	:set t_xy=^[foo;
+There is no warning for using a name that isn't recognized.  You can map these
+codes as you like: >
+	:map <t_xy> something
+<								*E846*
+When a key code is not set, it's like it does not exist.  Trying to get its
+value will result in an error: >
+	:set t_kb=
+	:set t_kb
+	E846: Key code not set: t_kb
+
 The t_xx options cannot be set from a |modeline| or in the |sandbox|, for
 security reasons.
 
diff --git a/src/option.c b/src/option.c
index f1fcd69..b633466 100644
--- a/src/option.c
+++ b/src/option.c
@@ -4352,7 +4352,7 @@
 		    p = find_termcode(key_name);
 		    if (p == NULL)
 		    {
-			errmsg = (char_u *)N_("E518: Unknown option");
+			errmsg = (char_u *)N_("E846: Key code not set");
 			goto skip;
 		    }
 		    else
@@ -4700,8 +4700,8 @@
 						|| s[i] == ','
 						|| s[i] == NUL))
 					break;
-				    /* Count backspaces.  Only a comma with an
-				     * even number of backspaces before it is
+				    /* Count backslashes.  Only a comma with an
+				     * even number of backslashes before it is
 				     * recognized as a separator */
 				    if (s > origval && s[-1] == '\\')
 					++bs;
diff --git a/src/version.c b/src/version.c
index d24bf7d..3505097 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    141,
+/**/
     140,
 /**/
     139,