WARNING: Invalid source IP www.mypage.com for test (null), using default

I'm using Hobbit 4.2.3 and for some pages, I monitore, I get the following message in bbtest.

WARNING: Invalid source IP www.mypage.com for test (null), using default

To be honest, I don't understand this error message, specially the "test (null)" Looks like there running something wrong with this test. I can ping the page from hobbit/xymon server and also other page monitoring is working well!