/* Defined in image.c */
extern Lisp_Object QCascent, QCmargin, QCrelief;
extern Lisp_Object QCconversion;
-extern int x_bitmap_mask (struct frame *, int);
+extern int x_bitmap_mask (struct frame *, ptrdiff_t);
extern void syms_of_image (void);
extern void init_image (void);