diff --git a/src/optionstr.c b/src/optionstr.c
index b1bb39a..ccba976 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -3904,17 +3904,16 @@
  * The 'termwinsize' option is changed.
  */
     char *
-did_set_termwinsize(optset_T *args UNUSED)
+did_set_termwinsize(optset_T *args)
 {
+    char_u	**varp = (char_u **)args->os_varp;
     char_u	*p;
 
-    if (*curwin->w_p_tws == NUL)
+    if ((*varp)[0] == NUL)
 	return NULL;
 
-    p = skipdigits(curwin->w_p_tws);
-    if (p == curwin->w_p_tws
-	    || (*p != 'x' && *p != '*')
-	    || *skipdigits(p + 1) != NUL)
+    p = skipdigits(*varp);
+    if (p == *varp || (*p != 'x' && *p != '*') || *skipdigits(p + 1) != NUL)
 	return e_invalid_argument;
 
     return NULL;
diff --git a/src/testdir/gen_opt_test.vim b/src/testdir/gen_opt_test.vim
index e855602..7b0064c 100644
--- a/src/testdir/gen_opt_test.vim
+++ b/src/testdir/gen_opt_test.vim
@@ -57,7 +57,6 @@
       \ sidescrolloff:	'TODO: fix missing error handling for setglobal',
       \ tabstop:	'TODO: fix missing error handling for setglobal',
       \ termwinkey:	'TODO: fix missing error handling for setglobal',
-      \ termwinsize:	'TODO: fix missing error handling for setglobal',
       \ textwidth:	'TODO: fix missing error handling for setglobal',
       \}
 
diff --git a/src/version.c b/src/version.c
index 7a0b0ad..404ebf5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    800,
+/**/
     799,
 /**/
     798,