```common lisp
(in-package #:sicl-global-environment)

(defconstant nil 'nil)
(defconstant t 't)
```

Use explicit package marker with IN-PACKAGE.
user
```common lisp
(cl:in-package #:sicl-global-environment)

(defconstant nil 'nil)
(defconstant t 't)
```
assistant