OpenWrt not accepting ',' symbol in password

I have LINKIT7688 with openwrt15.05 from manufacturer. I setup a WiFi AP with WPA2 password '12345678' and managed to connect to it from my LINKIT. When I change any of the symbols to ',' (comma). It does not manage to connect to the AP.
Problem is I cannot limit the user not to use commas in his passwords...
Please help..

(a) That's pretty ancient and almost certainly insecure due to its age
(b) OEM firmware based on OpenWrt is usually nothing like an OpenWrt release (it's a convenient starting point for a custom firmware, and, being GPL, doesn't cost them anything to use)

I'd suggest considering upgrading to current, "stock" OpenWrt