GWT Facet & Source Level

I have a client that has some GWT projects, and both myself and one of the client's onsite developers are using IntelliJ (the rest of the team is using Eclipse). The whole team is using JDK 8, but source level of JDK7, since the version of GWT they use doesn't support JDK 8 syntax.

If I look at a file containing a generics diamond, my IntelliJ warns me that the GWT Facet's source level doesn't allow diamonds:

The modules are all set to language level 7. I don't see a setting in the GWT Facet anywhere. The quick fix doesn't help. And yet, my colleague does not see the same warning, so somehow he isn't having the same problem. What do I need to change?