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java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState

Can you please provide more information? Plugin version,  IDEA version, build environment, code and steps to reproduce?

It's in oncreate probably. Make sure it's nullable. Newest support library in 27 has proper null annotations

If you override it on older versions where it's not specified, it'll throw an exception

<@U2SG23BPU> - IDEA version - 3.0.1
compileSdkVersion 27
kotlin Version = ‘1.1.51’
Steps to reproduce are just create a Custom dialog and call show method on it with Activity context
support lib -v7:27.0.0'

<@UA6EDAXD4> Yep, <@U2N3CF6D6> is right -- it's about new nullability annotations in android support library. They are supported only since Kotlin `1.2.31` that's why you don't get a safe typechecking from the compiler.