Run configuration not working

Well I'm impressed that IntelliJ imported my gradle Java 11 modular projects (100+ of them in multiple trees) without a hitch. In Eclipse I was pulling my hair out for a couple of solid days and it still didn't work. 

However, the easy thing I expected to work didn't. I created a run configuration for my application and passed the JVM argument -Xmx8g. Strangely, it was passed as an argument to the application instead of the JVM, which failed because it doesn't accept that switch. I thought surely I must have messed it up so I triple checked and yes, I definitely put the -Xmx8g under "VM options". Any ideas?