diff --git a/core/src/main/scala/org/apache/spark/rdd/EmptyRDD.scala b/core/src/main/scala/org/apache/spark/rdd/EmptyRDD.scala
index 22e8c8c54310b..a2d7e344cf1b2 100644
--- a/core/src/main/scala/org/apache/spark/rdd/EmptyRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/EmptyRDD.scala
@@ -24,7 +24,7 @@ import org.apache.spark.{Partition, SparkContext, TaskContext}
 /**
  * An RDD that has no partitions and no elements.
  */
-class EmptyRDD[T: ClassTag](sc: SparkContext) extends RDD[T](sc, Nil) {
+private[spark] class EmptyRDD[T: ClassTag](sc: SparkContext) extends RDD[T](sc, Nil) {
 
   override def getPartitions: Array[Partition] = Array.empty
 
diff --git a/core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala b/core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala
index a447030752096..98b44f724a838 100644
--- a/core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala
@@ -43,6 +43,7 @@ private[spark] class UnionPartition[T: ClassTag](idx: Int, rdd: RDD[T], splitInd
   }
 }
 
+/** <span class="badge" style="float: right; background-color: #44751E;">DEVELOPER API</span> */
 class UnionRDD[T: ClassTag](
     sc: SparkContext,
     @transient var rdds: Seq[RDD[T]])