diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/DataStreams.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/DataStreams.kt
index 0e5b6303e..516a47e4d 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/DataStreams.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/DataStreams.kt
@@ -76,7 +76,7 @@ val VarLongValueCodec = StreamCodec(DataInputStream::readVarLongLE, DataOutputSt
 val BinaryStringCodec = StreamCodec(DataInputStream::readBinaryString, DataOutputStream::writeBinaryString)
 
 class EnumValueCodec<V : Enum<V>>(clazz: Class<out V>, val writeByIndices: Boolean = false) : IStreamCodec<V> {
-	private val values = clazz.enumConstants
+	private val values = clazz.enumConstants ?: throw ClassCastException("$clazz does not have enum constants. Not an enum?")
 
 	override fun read(stream: DataInputStream): V {
 		if (writeByIndices) {