diff --git a/src/sudoku.s b/src/sudoku.s
index 063b49f..eb33d79 100644
--- a/src/sudoku.s
+++ b/src/sudoku.s
@@ -78,7 +78,8 @@ TOSLP:  ILDB  D,A                     ;Load the next character from A.
         SUBI  D,40                    ;Convert 32..95 to 0..63
         IDPB  D,B                     ;Deposit the character in the destination.
         JRST  TOSLP                   ;Repeat with next character.
-TOSEN:  POP   P,D                     ;Restore the D register.
+TOSEN:  IDPB  D,[000]                 ;Make sure the last char is 0
+        POP   P,D                     ;Restore the D register.
         POPJ  P,                      ;Return from function.
 
 ;Subroutine to print a string of text on the output.