In `getSourceRoots()` there is this code that refers to the `source` field from `SourceTask`: ```java for(Object obj : this.source) { if(obj instanceof SourceDirectorySet) { returnValues.addAll(((SourceDirectorySet) obj).getSrcDirs()); } } ``` The `source` field was exposed before as `protected`, but we are removing that in Gradle 5.0. Please use `getSource()` instead.