diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index db244f095a..e7d5ba728a 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -1005,6 +1005,10 @@ static int insert_handle_key(InsertState *s)
   }
 
   case K_COMPLETE_DELAY:  // 'autocompletedelay' expired
+    // If CTRL-G U was used apply it to the next typed key.
+    if (dont_sync_undo == kTrue) {
+      dont_sync_undo = kNone;
+    }
     ins_compl_clear_autocomplete_delay();
     if (!ins_compl_has_autocomplete() || char_avail() || curwin->w_cursor.col == 0) {
       break;
diff --git a/test/old/testdir/test_ins_complete.vim b/test/old/testdir/test_ins_complete.vim
index af4b7ccdc6..2acb1d0b40 100644
--- a/test/old/testdir/test_ins_complete.vim
+++ b/test/old/testdir/test_ins_complete.vim
@@ -6068,6 +6068,30 @@ func Test_autocompletedelay()
   call StopVimInTerminal(buf)
 endfunc
 
+func Run_test_autocompletedelay_ctrl_g_U(delay1, delay2)
+  new
+  call setline(1, 'foo bar baz')
+  inoremap <buffer> ( ()<C-g>U
+  set autocomplete autocompletedelay=200
+
+  call timer_start(a:delay1, { -> feedkeys('(', 't') })
+  call timer_start(a:delay2, { -> feedkeys("\<Left>a\<Esc>", 't') })
+  call feedkeys('ob', 'tx!')
+  call assert_equal(['foo bar baz', 'b(a)'], getline(1, '$'))
+  undo
+  call assert_equal(['foo bar baz'], getline(1, '$'))
+
+  set autocomplete& autocompletedelay&
+  bwipe!
+endfunc
+
+func Test_autocompletedelay_ctrl_g_U()
+  " '(' typed after 'autocompletedelay' expires
+  call Run_test_autocompletedelay_ctrl_g_U(250, 500)
+  " '(' typed before 'autocompletedelay' expires
+  call Run_test_autocompletedelay_ctrl_g_U(150, 500)
+endfunc
+
 " Preinsert longest prefix when autocomplete
 func Test_autocomplete_longest()
   func GetLine()