bug "$message" literal in commit message

Hello,

I think I found a bug(or strange behavior) in the git.
If commit message contains literal "$message" than that literal
disappears from commit message.

For example:
-------------
user@comp ~/cc $ git commit -am "1$message1"
[master (root-commit) d36a841] 1
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 1

user@comp ~/cc $ git log
commit d36a841ae25510ada80246a78225446083fcb3e1
Author: user [off-list ref]
Date:   Wed Jun 3 18:21:45 2015 +0200

    file
----------------

Sorry for having disturbed you