Took me a while to aggregate an actual solution, but here's how to get rid of this compile error.
Open IntelliJ preferences.
Search for "compiler" (or something like "compi").
Scroll down to Maven -->java compiler. In the right panel will be a list of modules and their associated java compile version "target bytecode version."
Select a version >1.5. You may need to upgrade your jdk if one is not available.