After upgrading to 1 5 0 from 1 4 3 I got this error ```Caus

Question

After upgrading to 1 5 0 from 1 4 3 I got this error ```Caused by kotlinx serialization SerializationException Class ArrayList is not registered for polymorphic serialization in the scope of Collection ``` Partial stacktrace ```kotlinx serialization SerializationException Class ArrayList is not registered for polymorphic serialization in the scope of Collection Mark the base class as sealed or register the serializer explicitly at kotlinx serialization internal AbstractPolymorphicSerializerKt throwSubtypeNotRegistered AbstractPolymorphicSerializer kt 103 at kotlinx serialization internal AbstractPolymorphicSerializerKt throwSubtypeNotRegistered AbstractPolymorphicSerializer kt 113 at kotlinx serialization PolymorphicSerializerKt findPolymorphicSerializer PolymorphicSerializer kt 96 at kotlinx serialization internal AbstractPolymorphicSerializer serialize AbstractPolymorphicSerializer kt 32 at kotlinx serialization json internal StreamingJsonEncoder encodeSerializableValue StreamingJsonEncoder kt 223 at kotlinx serialization json Json encodeToString Json kt 73 at io ktor serialization SerializationConverter convertForSend SerializationConverter kt 118 at io ktor features ContentNegotiation$Feature$install$2 invokeSuspend ContentNegotiation kt 146 at io ktor features ContentNegotiation$Feature$install$2 invoke ContentNegotiation kt ```

Jose A. · Answer

The new version forgot how to convert a list

Jose A. · Answer

``` install ContentNegotiation val jsonConfig = Json DefaultJson encodeDefaults = false json jsonConfig ``` This is the way I install the feature just using `json `fails too

Jose A. · Answer

Going back to 1 4 3 fixes the error

e5l · Answer

Hey < Jose A > thanks for the notice Could you file an issue

Jose A. · Answer

Will do

Rustam Siniukov · Answer

< Jose A > Can you please post type of the response here

Jose A. · Answer

``` get list val response Collection lt String gt = listOf a b call respond response ```

Jose A. · Answer

This triggers the exception So Collection lt String gt

Jose A. · Answer

I just posted the problem here <https youtrack jetbrains com issue KTOR 1795>

Joost Klitsie · Answer

Did you try cleaning invalidating cache

Jose A. · Answer

Same result

Rustam Siniukov · Answer

opened PR with the fix target 1 5 1

Rustam Siniukov · Answer

thanks for the report

Jose A. · Answer

Thanks for the fast response