Non numeric move to comp-3 field does not give a system completion

I have a program which allows a non-numeric move
to a comp-3 field without a 0C7 error.
Would anyone know why ?

TIA
David


03 WHJ1-DSPLY-INVC-ARGT-ID        PIC X(10)   VALUE SPACES
10 AAWFQ-INVC-ARGT-ID             PIC S9(10) COMP-3.


DISPLAY 'WHJ1-DSPLY-INVC-ARGT-ID = ' WHJ1-DSPLY-INVC-ARGT-ID
MOVE WHJ1-DSPLY-INVC-ARGT-ID      TO AAWFQ-INVC-ARGT-ID
DISPLAY 'AAWFQ-INVC-ARGT-ID      = ' AAWFQ-INVC-ARGT-ID


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Display  Filter  View  Print  Options  Help
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SDSF OUTPUT DISPLAY SFLOINC1 JOB24659  DSID   12
COMMAND INPUT ===>
WHJ1-DSPLY-INVC-ARGT-ID = 008A500000
 ECDF6CEDDE6CDEC6CDCE6CC474FFFCFFFFFF4444
444444444
 681104273809553019730940E000815000000000
000000000
------------------------------------------------
AAWFQ-INVC-ARGT-ID      = 0081500000
 CCECD6CDEC6CDCE6CC44444474FFFFFFFFFF4444
444444444
 116680955301973094000000E000815000000000
000000000
------------------------------------------------