lua-mode has derived from prog-mode for a while now.

diff --git a/pico8.el b/pico8.el
index bc3ce11..32239f5 100644 (file)
--- a/pico8.el
+++ b/pico8.el
@@ -454,9 +454,8 @@ this is the numeric literal in the code."
     (let ((beg (- (point) (% (min 255 (current-column)) 2))))
       (string-to-number (buffer-substring beg (+ beg 2)) 16)))
 
-   ;; In Lua or other code, the sprite is a numeric literal.
-   ;; lua-mode doesn't derive from anything.
-   ((or (derived-mode-p 'lua-mode) (derived-mode-p 'prog-mode))
+   ;; In Lua, the sprite is a numeric literal.
+   ((derived-mode-p 'lua-mode)
     (pico8--string-to-number (or (word-at-point) "")))
 
    (t nil)))