diff --git a/src/getchar.c b/src/getchar.c
index e208dd1..e6879c6 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -2363,7 +2363,7 @@
  * into just a key, apply that.
  * Check from typebuf.tb_buf[typebuf.tb_off] to typebuf.tb_buf[typebuf.tb_off
  * + "max_offset"].
- * Return the length of the replaced bytes, zero if nothing changed.
+ * Return the length of the replaced bytes, 0 if nothing changed, -1 for error.
  */
     static int
 check_simplify_modifier(int max_offset)
@@ -2397,7 +2397,15 @@
 		    vgetc_char = c;
 		    vgetc_mod_mask = tp[2];
 		}
-		len = mb_char2bytes(new_c, new_string);
+		if (IS_SPECIAL(new_c))
+		{
+		    new_string[0] = K_SPECIAL;
+		    new_string[1] = K_SECOND(new_c);
+		    new_string[2] = K_THIRD(new_c);
+		    len = 3;
+		}
+		else
+		    len = mb_char2bytes(new_c, new_string);
 		if (modifier == 0)
 		{
 		    if (put_string_in_typebuf(offset, 4, new_string, len,
@@ -2424,6 +2432,7 @@
  * - When nothing mapped and typeahead has a character: return map_result_get.
  * - When there is no match yet, return map_result_nomatch, need to get more
  *   typeahead.
+ * - On failure (out of memory) return map_result_fail.
  */
     static int
 handle_mapping(
@@ -2706,7 +2715,12 @@
 	    // If no termcode matched, try to include the modifier into the
 	    // key.  This is for when modifyOtherKeys is working.
 	    if (keylen == 0 && !no_reduce_keys)
+	    {
 		keylen = check_simplify_modifier(max_mlen + 1);
+		if (keylen < 0)
+		    // ins_typebuf() failed
+		    return map_result_fail;
+	    }
 
 	    // When getting a partial match, but the last characters were not
 	    // typed, don't wait for a typed character to complete the
diff --git a/src/term.c b/src/term.c
index 14cee6a..ee8be7f 100644
--- a/src/term.c
+++ b/src/term.c
@@ -4531,7 +4531,9 @@
 	    del_typebuf(-extra, offset);
 	else if (extra > 0)
 	    // insert the extra space we need
-	    ins_typebuf(string + slen, REMAP_YES, offset, FALSE, FALSE);
+	    if (ins_typebuf(string + slen, REMAP_YES, offset, FALSE, FALSE)
+								       == FAIL)
+		return FAIL;
 
 	// Careful: del_typebuf() and ins_typebuf() may have reallocated
 	// typebuf.tb_buf[]!
diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index ddbe707..c9b0c7b 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -2439,8 +2439,9 @@
 
 func Test_simplify_ctrl_at()
   " feeding unsimplified CTRL-@ should still trigger i_CTRL-@
-  call feedkeys("ifoo\<Esc>A\<*C-@>", 'xt')
-  call assert_equal('foofoo', getline(1))
+  call feedkeys("ifoo\<Esc>A\<*C-@>x", 'xt')
+  call assert_equal('foofo', getline(1))
+  bw!
 endfunc
 
 
diff --git a/src/version.c b/src/version.c
index 115989c..a8f6671 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4833,
+/**/
     4832,
 /**/
     4831,