Just a note for the uninitiated: when you pin from Stable you just gave up the guarantees that may have been the reason you were on Stable in the first place. This is an area where RTFM is in order:
"WARNING: Use of apt-pinning by a novice user is sure call for major troubles. You must avoid using apt-pinning except when you absolutely need it." https://www.debian.org/doc/manuals/debian-reference/ch02.en....