Appeal by defendant from two judgments of the Supreme Court, Richmond County (Barlow, J.), each rendered December 27, 1978, convicting him on indictment number 48/78 of robbery in the first degree and grand larceny in the second degree, upon a jury verdict, convicting him on indictment number 49/78 of attempted robbery in the third degree, upon his plea of guilty, and imposing sentences as a second felony offender, and from an amended judgment of the same court (Di Vernieri, J.), adjudicating him in violation of probation, upon his plea of guilty, and imposing sentence to a term of imprisonment under indictment number 127/77. Judgments and amended judgment affirmed. When defendant was sentenced as a second felony offender he was advised that the prosecutor had filed a statement pursuant to CPL 400.21 setting forth his prior felony conviction, upon his plea of guilty, of robbery in the third degree, by judgment of the Supreme Court, Richmond County, rendered September 7, 1977. By admitting the truth of the allegations in the second felony offender statement at the time the sentences were imposed, defendant waived any objections he might have had to the use of that prior felony conviction as a basis for adjudicating him a predicate felon (CPL 400.21, subds 3, 4). Thus, he waived his claim that his guilty plea to robbery in the third degree was not voluntarily and knowingly entered because he was not advised of his right to confront witnesses and his privilege against self incrimination (CPL 400.21, subd 7, par [b]; see People v Bryant, 47 A.D.2d 51, 62-63). Defendant's claim that his counsel's failure to request a second felony offender hearing denied him effective assistance of counsel is dependent upon facts dehors the record and must "be proved, if at all * * * in a proceeding maintainable under CPL [article] 440" (see People v Johnson, 51 N.Y.2d 986, 988). We have considered defendant's other contention and find it to be without merit. Weinstein, J.P., Bracken, Brown and Niehoff, JJ., concur.