RowCoder not equal after serialization

import org.apache.beam.sdk.coders._
import org.apache.beam.sdk.schemas.Schema

val schema =
      Schema
        .builder()
        .addInt32Field("c1")
        .addStringField("c2")
        .addDoubleField("c3")
        .build()

val coder = RowCoder.of(schema)
org.apache.beam.sdk.util.SerializableUtils.ensureSerializable(coder)

java.lang.IllegalStateException: Coder not equal to original after serialization, indicating that the Coder may not implement serialization correctly.  Before: org.apache.beam.sdk.coders.RowCoder@1323050e, after: org.apache.beam.sdk.coders.RowCoder@4c03150a