diff --git a/asminc/atari.inc b/asminc/atari.inc
index b8f883cd8..f7a7ab223 100644
--- a/asminc/atari.inc
+++ b/asminc/atari.inc
@@ -1021,6 +1021,7 @@ XGLIN        = $0871    ; get line
 XSKIP        = $0874    ; skip parameter
 XMOVE        = $0877    ; move filename
 XGNUM        = $087A    ; get number
+XDEFDEV      = $0816    ; current drive * undocumented *
 
 ;-------------------------------------------------------------------------
 ; End of atari.inc
diff --git a/libsrc/atari/getdefdev.s b/libsrc/atari/getdefdev.s
index 280c042e5..56ad8ff65 100644
--- a/libsrc/atari/getdefdev.s
+++ b/libsrc/atari/getdefdev.s
@@ -27,9 +27,10 @@
 __getdefdev:
 
         lda     __dos_type      ; which DOS?
-        cmp     #OSADOS+1
-        bcs     finish          ; only supported on OS/A+ and SpartaDOS
-                                ; (TODO: add XDOS support)
+        cmp     #XDOS
+        beq     xdos            ; only supported on XDOS ...
+;       cmp     #OSADOS+1       ; (redundant: #OSADOS+1 = #XDOS)
+        bcs     finish          ; ... and on OS/A+ and SpartaDOS
 
         ldy     #BUFOFF
         lda     #0
@@ -68,7 +69,7 @@ crvec:  jsr     $FFFF           ; will be set to crunch vector
         sta     __defdev
         iny
         lda     (DOSVEC),y
-        sta     __defdev+1
+done:   sta     __defdev+1
 
 ; Return pointer to default device
 
@@ -76,6 +77,11 @@ finish: lda     #<__defdev
         ldx     #>__defdev
         rts
 
+; XDOS version
+
+xdos:   lda     XDEFDEV
+        bne     done
+
         .data
 
 ; Default device