problem with crypto++ ECIES BERDecodePrivateKey

I'm trying to Store ECIES num0 PrivateKey with DEREncodePrivateKey to a std::string and reload it in num1 PrivateKey Object for testing. Problem is when key is loaded with BERDecodePrivateKey in second PrivateKey object it can't be validated (also tested encryption and decrypting without validation and didn't decrypt )

here's the code

    using namespace CryptoPP;
        CryptoPP::AutoSeededRandomPool prng;

        ECIES<ECP>::PrivateKey pp; 
        pp.Initialize(prng, ASN1::secp256k1());
/* returns true*/
        bool val=pp.Validate(prng, 3);

        std::string saves;
        StringSink savesink(saves);
        pp.DEREncodePrivateKey(savesink);
/*additional unnecessary steps to make sure the key is written completely */
        savesink.MessageEnd();
        savesink.Flush(true);   

        ECIES<ECP>::PrivateKey pro;
        StringSource savesSource(saves, true);
        pro.BERDecodePrivateKey(savesSource,true,savesSource.MaxRetrievable());
/*here the exception is thrown */
        pro.ThrowIfInvalid(prng, 3);

finally found what the problem is as @maarten-bodewes mentioned in comment the DER encoded private exponent doesn't determine the curve OID for the privateKey Object , so before BER Decoding and importing key we need to somehow determine the OID for the Object; the simplest way is to determine it when Initializing new Object above code changes to :

ECIES<ECP>::PrivateKey pro;
    StringSource savesSource(saves, true);
    auto rett = savesSource.MaxRetrievable();
    pro.Initialize(prng, ASN1::secp256k1());
    pro.BERDecodePrivateKey(savesSource,true,savesSource.MaxRetrievable());

also you AccessGroupParameters().Initialize(/*OID*/); or Initialize(/*OID*/) for existing object