ORA-01031 and compile public synonym object

 Hy,

I get ORA-01031 when I try to compile a public synonym object :

alter public SYNONYM PT1XXXX compile;
*
ERREUR Á la ligne 1 :
ORA-01031: privilÒges insuffisants

(I have DBA role  and I am the PT1XXXX object's owner)

But when when I try to compile

with sqlplus / as sysdba  It's OK :

 alter public SYNONYM PT1XXXXcompile;

Synonyme modifiÕ. 

Who can help me ?

Regards

ERIC