diff --git a/libsrc/atari/dioqsize.s b/libsrc/atari/dioqsize.s
new file mode 100644
index 000000000..0c2c47bda
--- /dev/null
+++ b/libsrc/atari/dioqsize.s
@@ -0,0 +1,27 @@
+;
+; Christian Groessler, February 2005
+;
+; sectsize_t __fastcall__ dio_query_sectsize(dhandle_t handle);
+;
+
+	.include	"atari.inc"
+	.export		_dio_query_sectsize
+	.importzp	ptr1,tmp1
+	.import		popax, __oserror
+
+.proc	_dio_query_sectsize
+
+	sta	ptr1		; handle
+	stx	ptr1+1 
+
+	lda	#0
+	sta	__oserror
+
+	ldy	#sst_sectsize+1
+	lda	(ptr1),y
+	tax
+	dey
+	lda	(ptr1),y
+	rts
+
+.endproc