Bug with Kotlin + Moshi

Bug.kt

import com.squareup.moshi.Json
import com.squareup.moshi.KotlinJsonAdapterFactory
import com.squareup.moshi.Moshi
import org.junit.Test

data class DataClass(
        @Json(name = "par1") val par1: String?,
        @Json(name = "par2") val par2: String?,
        @Json(name = "par3") val par3: String?,
        @Json(name = "par4") val par4: String?,
        @Json(name = "par5") val par5: String?,
        @Json(name = "par6") val par6: String?,
        @Json(name = "par7") val par7: String?,
        @Json(name = "par8") val par8: String?,
        @Json(name = "par9") val par9: String?,
        @Json(name = "par10") val par10: String?,
        @Json(name = "par11") val par11: String?,
        @Json(name = "par12") val par12: String?,
        @Json(name = "par13") val par13: String?,
        @Json(name = "par14") val par14: String?,
        @Json(name = "par15") val par15: String?,
        @Json(name = "par16") val par16: String?,
        @Json(name = "par17") val par17: String?,
        @Json(name = "par18") val par18: String?,
        @Json(name = "par19") val par19: String?,
        @Json(name = "par20") val par20: String?,
        @Json(name = "par21") val par21: String?,
        @Json(name = "par22") val par22: String?,
        @Json(name = "par23") val par23: String?,
        @Json(name = "par24") val par24: String?,
        @Json(name = "par25") val par25: String?,
        @Json(name = "par26") val par26: String?,
        @Json(name = "par27") val par27: String?,
        @Json(name = "par28") val par28: String?,
        @Json(name = "par29") val par29: String?,
        @Json(name = "par30") val par30: String?,
        @Json(name = "par31") val par31: String?,
        @Json(name = "par32") val par32: String?,
        @Json(name = "par33") val par33: String?
)

val json = """
{
 "par1": "val1",
 "par2": "val2",
 "par3": "val3",
 "par4": "val4",
 "par5": "val5",
 "par6": "val6",
 "par7": "val7",
 "par8": "val8",
 "par9": "val9",
 "par10": "val10",
 "par11": "val11",
 "par12": "val12",
 "par13": "val13",
 "par14": "val14",
 "par15": "val15",
 "par16": "val16",
 "par17": "val17",
 "par18": "val18",
 "par19": "val19",
 "par20": "val20",
 "par21": "val21",
 "par22": "val22",
 "par23": "val23",
 "par24": "val24",
 "par25": "val25",
 "par26": "val26",
 "par27": "val27",
 "par28": "val28",
 "par29": "val29",
 "par30": "val30",
 "par31": "val31",
 "par32": "val32",
 "par33": "val33"
}
"""

class Tests {

    @Test
    fun bug() {
        val moshi = Moshi.Builder().add(KotlinJsonAdapterFactory()).build()
        val jsonAdapter = moshi.adapter(DataClass::class.java)
        val dataClass = jsonAdapter.fromJson(json)
        System.out.println(dataClass)
    }
}