GWT compiler is running out of memory. How do I configure it within IntelliJ?

I'm running GWT from within IntelliJ. (Plain GWT, IntelliJ v9). I'm able to run my application via my "GWT development mode" configuration, but when I try to run it through my "local tomcat" configuration, I get a bunch of incomprehensible error messages referring to Oracle and all sorts of weird stuff that I don't use, followed by this error which is sorted to the bottom of all the others:

Error: Out of memory; to increase the amount of memory, use the -Xmx flag at startup (java -Xmx128M ...)

I'm guessing that this error is the root cause.

According to my understanding, there is a GWT compilation step which runs in a JVM separate to both IntelliJ and tomcat, and so I'm unsure where to set the -Xmx parameter.

My question is: where do I find this -Xmx parameter? (And: am I on the right track, taking this error message at face value, or is it a symptom of deeper problems?)

You can configure the heap in the GWT facet settings: