Hello, I am using Transfer After Bridge in Bypass media mode and when I transfer I am getting this error

2015-09-20 22:22:14.278228 [ERR] switch_core_io.c:187 sofia/internal/xxxx has no read codec.

Does anyone know what this error means and how to correct it? I didn’t know codec was needed in bypass mode.  I am transferring back to the dial plan.

Thanks