diff --git a/core/src/main/scala/org/apache/spark/SparkEnv.scala b/core/src/main/scala/org/apache/spark/SparkEnv.scala
index e4e1f5e6378da..40a1d2d0a9614 100644
--- a/core/src/main/scala/org/apache/spark/SparkEnv.scala
+++ b/core/src/main/scala/org/apache/spark/SparkEnv.scala
@@ -42,6 +42,9 @@ import org.apache.spark.util.{AkkaUtils, Utils}
  * Spark code finds the SparkEnv through a thread-local variable, so each thread that accesses these
  * objects needs to have the right SparkEnv set. You can get the current environment with
  * SparkEnv.get (e.g. after creating a SparkContext) and set it with SparkEnv.set.
+ *
+ * NOTE: This is not intended for external use. This is exposed for Shark and may be made private
+ *       in a future release.
  */
 @DeveloperApi
 class SparkEnv (