Animate CC 1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.

When I play my game (With this script being the only script)

import flash.events.KeyboardEvent;
import flash.events.Event;
stop();
//Character
var charSpeed: Number = 0
var ySpeed: Number = 0
var jumping: Boolean = false
//World
var gravity: Number = 1
//Events
stage.addEventListener(KeyboardEvent.KEY_DOWN, btnPress);
stage.addEventListener(KeyboardEvent.KEY_UP, btnRelease);
stage.addEventListener(Event.ENTER_FRAME, loop);
function btnPress(event: KeyboardEvent): void {
  if (event.KeyCode == Keyboard.LEFT) {
  charSpeed = -5;
  }
  if (event.KeyCode == Keyboard.RIGHT) {
  charSpeed = 5;
  }
  if (event.KeyCode == Keyboard.UP) {
  if (!jumping)
  ySpeed = -14
  jumping = true
  }
}
function btnRelease(event: KeyboardEvent) {
  if (event.KeyCode == Keyboard.LEFT) {
  charSpeed = 0;
  }
  if (event.KeyCode == Keyboard.RIGHT) {
  charSpeed = 0;
  }
}
function loop(e: Event) {
char.x += charSpeed;
if (char.x < -25) {
char.x = -25;
}
if (char.x > 1225) {
char.x = 1225
}
}

I get the following errors:

Scene 1, Layer 'Background&Var', Frame 1, Line 22, Column 12
1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.
Scene 1, Layer 'Background&Var', Frame 1, Line 25, Column 12
1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.
Scene 1, Layer 'Background&Var', Frame 1, Line 28, Column 12
1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.
Scene 1, Layer 'Background&Var', Frame 1, Line 36, Column 12
1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.
Scene 1, Layer 'Background&Var', Frame 1, Line 39, Column 12
1119: Access of possibly undefined property KeyCode through a reference with static type flash.events:KeyboardEvent.

Do any of you guys have any idea on how to fix this?

Any help would be greatly appreciated.