I'm using kotlinx.serialization (JVM) for JSON deserialization, and I'm getting this error when I make a GET request:

java.lang.UnsupportedOperationException: The only generic classes supported for now are standard collections, got class class ResponseEnvelope

It looks like the solution to this was to use

KotlinxSerializer.setMapper(...)

in the

HttpClientConfig

, but that's been deprecated. Here is the erroring line of code: https://github.com/BenWoodworth/GroupMe.kt/tree/63b918c8d5a6c0a4aa3316ab76214beb72986e3d/src/main/kotlin/net/benwoodworth/groupme/GroupMe.kt#L75 Here is ResponseEnvelope, the class I want to deserialize: https://github.com/BenWoodworth/GroupMe.kt/tree/63b918c8d5a6c0a4aa3316ab76214beb72986e3d/src/main/kotlin/net/benwoodworth/groupme/ResponseEnvelope.kt Here is the ktor HttpClient declaration: https://github.com/BenWoodworth/GroupMe.kt/tree/63b918c8d5a6c0a4aa3316ab76214beb72986e3d/src/main/kotlin/net/benwoodworth/groupme/GroupMe.kt#L53-L61 And here is my build.gradle: https://github.com/BenWoodworth/GroupMe.kt/tree/63b918c8d5a6c0a4aa3316ab76214beb72986e3d/build.gradle Any idea how I might be able to fix this?

setMapper

wouldn't help here anyway. You'll have to pass in the serializer at call site. I'll find you an example.