How to define key mapping of esc under helm-mode

Hi, I tried this mapping: (define-key helm-map "\e" 'helm-keyboard-quit) But it doesn't work. However, (define-key helm-map "qq" 'helm-keyboard-quit) works. I'd suspect something's wrong with the special esc key. Regards. -- 吾輩は猫である。ホームーページはhttps://introo.me <http://introo.me>。