Unable to create CertificationRequestInfo because of some problem in ASN1Set attribute- attrs

I am trying to create a certification request ( to eventually generateCSR) using challenge passcode which I get from a SCEP server. But there is some issue with the attrs object and so the certification request is not getting created.

The code I wrote-

ASN1Encodable[] attrValues = new ASN1Encodable[1];
attrValues[0] = new Attribute(PKCSObjectIdentifiers.pkcs_9_at_challengePassword, new DERSet(new DERPrintableString(challenge)));
ASN1Set attrs = new DERSet(attrValues);
CertificationRequestInfo requestInfo = new CertificationRequestInfo(new X500Name(subject), pkInfo, attrs);

The error Im getting-

Exception in thread "main" java.lang.IllegalArgumentException: unknown object in factory: org.bouncycastle.asn1.x509.Attribute
        at org.bouncycastle.asn1.pkcs.Attribute.getInstance(Attribute.java:37)
        at org.bouncycastle.asn1.pkcs.CertificationRequestInfo.validateAttributes(CertificationRequestInfo.java:159)
        at org.bouncycastle.asn1.pkcs.CertificationRequestInfo.<init>(CertificationRequestInfo.java:81)

I put empty DERSet instead of attrs the CSR gets generated- CertificationRequestInfo requestInfo = new CertificationRequestInfo(new X500Name(subject), pkInfo, new DERSet());

Can some please tell me where I'm going wrong?

You are using (probably due to an import) org.bouncycastle.asn1.x509.Attribute instead of org.bouncycastle.asn1.pkcs.Attribute. Although implementing the same functionality (and I'm not sure why it is duplicated), these are different classes.