Turn signal issue

My basically stock 99 XJ exhibits an unusual turn signal pattern. When the left turn signal is turned on, the front left signal light comes on normally, the left dash signal light comes on normally, however, BOTH rear signal lights flash. Right turn signals operate normally. The flasher works normally.

Any ideas on how to fix this issue would be appreciated.
:wierd:

OK. I'm new to the forums, and now that I have searched a little, I found the answer to my question in previous posts. I will replace the switch.

sounds like the switch. I have been looking into this too and need to replace mine now.