diff --git a/libsrc/atari/atari.inc b/libsrc/atari/atari.inc
index ef1437584..6d5a87d5c 100644
--- a/libsrc/atari/atari.inc
+++ b/libsrc/atari/atari.inc
@@ -1034,6 +1034,21 @@ ATDRW	= $1D		;DOWN-ARROW
 ATLRW	= $1E		;LEFT-ARROW
 ATRRW	= $1F		;RIGHT-ARROW
 
+;-------------------------------------------------------------------------
+; OFFSETS INTO SECTSIZETAB (DIO functions)
+;-------------------------------------------------------------------------
+
+sst_flag     = 0	; length 1
+sst_sectsize = 1	;        2
+sst_driveno  = 3	;        1  (drive #)
+;sst_id	     = 3	;        1  (to make size power of 2, used as
+;;				    test for valid pointer, must contain
+;;				    $CD)
+;SSTIDVAL     = $CD
+
+sst_size     = 4	; size of one entry
+			; if changed, adapt diopncls.s
+
 ;-------------------------------------------------------------------------
 ; End of atari.inc
 ;-------------------------------------------------------------------------