diff --git a/core/src/main/scala/org/apache/spark/SparkEnv.scala b/core/src/main/scala/org/apache/spark/SparkEnv.scala
index 8dfa8cc4b5b3fbd2d8ae0db307adc9257bf3da28..2b636b085d73aa26a8491adec34157ff267ebe08 100644
--- a/core/src/main/scala/org/apache/spark/SparkEnv.scala
+++ b/core/src/main/scala/org/apache/spark/SparkEnv.scala
@@ -183,6 +183,7 @@ object SparkEnv extends Logging {
 
     val serializer = instantiateClass[Serializer](
       "spark.serializer", "org.apache.spark.serializer.JavaSerializer")
+    logDebug(s"Using serializer: ${serializer.getClass}")
 
     val closureSerializer = instantiateClass[Serializer](
       "spark.closure.serializer", "org.apache.spark.serializer.JavaSerializer")