Possible bug, saved WEP security network will try to associate with SAME SSID but wpa security network

[Zheng BaoZhong-E13358]

Hi, all
 
Does it be possible bug?
 
I tested with wpa_supplicant 0.5.11 and 0.6.9, same behavior.
 
I have one AP with "test" SSID, and wpapsk security.
 
I add one network with "test" SSID and WEP security.