Undefined step definitions not highlighted in Cucumber/Gherkin

Hello,

I have been writing acceptance tests for my Java application with Cucumber/Gherkin. Recently, IntelliJ has stopped highlighting undefined step definitions in Cucumber, meaning that I can no longer hit Alt + Enter to create a new step definition. 

I have tried invalidating caches and restarting, and disabling and reenabling the Cucumber and Gherkin plugins. 

Has anyone experienced this before, and has any idea how to go about fixing it?

Thanks!