Handling phone links in uiwebview

[dacapo]

I'm doing a project for someone, and ran into an issue that I can't reproduce on my side but apparently happens when he runs it.

I'm using a 3GS 4.0.1 as my test device.
He is using a 4S 5.0.1 as his test device.

So, we have a basic uiwebview in one of the screens, and there is a phone number 01 23 456 789 that detects correctly in my environment and pops up a system "Cancel" or "Call" alertview. He is finding that on his phone, it just directly brings up the phone app without that alertview. He would definitely like it to prompt the user rather than to auto-launch the phone app.

Has anyone else run into this? Is it an iOS 5 issue, or is there something else I should be looking for?