diff --git a/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala b/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala
index 4344f851d9bc1812e616e3da0f4ab896dbddc173..77a39c71ed2c1d22a18a3af76c4cf5b7ef96ca5b 100644
--- a/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala
+++ b/core/src/main/scala/org/apache/spark/storage/MemoryStore.scala
@@ -33,7 +33,7 @@ private class MemoryStore(blockManager: BlockManager, maxMemory: Long)
   case class Entry(value: Any, size: Long, deserialized: Boolean)
 
   private val entries = new LinkedHashMap[String, Entry](32, 0.75f, true)
-  private var currentMemory = 0L
+  @volatile private var currentMemory = 0L
   // Object used to ensure that only one thread is putting blocks and if necessary, dropping
   // blocks from the memory store.
   private val putLock = new Object()
@@ -160,8 +160,10 @@ private class MemoryStore(blockManager: BlockManager, maxMemory: Long)
     putLock.synchronized {
       if (ensureFreeSpace(blockId, size)) {
         val entry = new Entry(value, size, deserialized)
-        entries.synchronized { entries.put(blockId, entry) }
-        currentMemory += size
+        entries.synchronized {
+          entries.put(blockId, entry)
+          currentMemory += size
+        }
         if (deserialized) {
           logInfo("Block %s stored as values to memory (estimated size %s, free %s)".format(
             blockId, Utils.bytesToString(size), Utils.bytesToString(freeMemory)))