diff --git a/src/sudoku.s b/src/sudoku.s
index 66743b7..2d5aca6 100644
--- a/src/sudoku.s
+++ b/src/sudoku.s
@@ -139,7 +139,7 @@ IMPRTF: PUSH  P,A                      ;Save the A register.
         MOVE  X,[440400,,FIELD]        ;Init a 4-bit byte pointer to FIELD.
         .CALL [SETZ ? SIXBIT/OPEN/     ;Open a file descriptor.
             [.UAI,,CHDSKI] ? [SIXBIT/DSK/] ;Mode, channel and device name
-            A ? B ((SETZ))]
+            [0,,A] ? [0,,B] ((SETZ))]
          .LOSE %LSFIL                  ;Handle errors after opening the file
 IMPRD:  .IOT  CHDSKI,A                 ;Read an ascii char into A.
         JUMPL A,IMPREX                 ;If there was nothing read, exit.