diff --git a/streaming/src/test/scala/org/apache/spark/streaming/rdd/WriteAheadLogBackedBlockRDDSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/rdd/WriteAheadLogBackedBlockRDDSuite.scala
index d2b983c4b4d1..5d8b0f5a4994 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/rdd/WriteAheadLogBackedBlockRDDSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/rdd/WriteAheadLogBackedBlockRDDSuite.scala
@@ -137,7 +137,8 @@ class WriteAheadLogBackedBlockRDDSuite extends FunSuite with BeforeAndAfterAll {
       blockIds: Seq[BlockId]
     ): Seq[WriteAheadLogFileSegment] = {
     require(blockData.size === blockIds.size)
-    val writer = new WriteAheadLogWriter(new File(dir, Random.nextString(10)).toString, hadoopConf)
+    val writer = new WriteAheadLogWriter(
+      new File(dir, Random.alphanumeric.take(10).mkString).toString, hadoopConf)
     val segments = blockData.zip(blockIds).map { case (data, id) =>
       writer.write(blockManager.dataSerialize(id, data.iterator))
     }