My RoR server receives a string, that was encrypted in C++ application using des3 with base64 encoding

The cipher object is created so:

cipher = OpenSSL::Cipher::Cipher::new("des3")
cipher.key = key_str
cipher.iv =  iv_str

key_str and iv_str: are string representations of key and initialization vector for encryption algorithm. They are the same for RoR and C++ application.

The code on the RoR side is following:

result = ""
result << cipher.update( Base64.decode64(message) )
result << cipher.final

After executing the last line of code, i get an exception

OpenSSL::CipherError (bad decrypt)

What is wrong here ? Any ideas ?