diff --git a/core/src/main/scala/org/apache/spark/util/collection/SizeTrackingPairBuffer.scala b/core/src/main/scala/org/apache/spark/util/collection/SizeTrackingPairBuffer.scala
index ef9761f607c39..9e9c16c5a2962 100644
--- a/core/src/main/scala/org/apache/spark/util/collection/SizeTrackingPairBuffer.scala
+++ b/core/src/main/scala/org/apache/spark/util/collection/SizeTrackingPairBuffer.scala
@@ -23,7 +23,7 @@ import java.util.Comparator
  * Append-only buffer of key-value pairs that keeps track of its estimated size in bytes.
  */
 private[spark] class SizeTrackingPairBuffer[K, V](initialCapacity: Int = 64)
-  extends SizeTrackingPairCollection[K, V] with SizeTracker
+  extends SizeTracker with SizeTrackingPairCollection[K, V]
 {
   require(initialCapacity <= (1 << 29), "Can't make capacity bigger than 2^29 elements")
   require(initialCapacity >= 1, "Invalid initial capacity")
diff --git a/core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala b/core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala
index e1004e9355532..ddb5df40360e9 100644
--- a/core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala
+++ b/core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala
@@ -109,7 +109,7 @@ class ExternalSorterSuite extends FunSuite with LocalSparkContext {
 
     val agg = new Aggregator[Int, Int, Int](i => i, (i, j) => i + j, (i, j) => i + j)
     val ord = implicitly[Ordering[Int]]
-    val elements = Iterator((1, 1), (5, 5)) ++ (0 until 50000).iterator.map(x => (2, 2))
+    val elements = Iterator((1, 1), (5, 5)) ++ (0 until 100000).iterator.map(x => (2, 2))
 
     val sorter = new ExternalSorter[Int, Int, Int](
       None, Some(new HashPartitioner(7)), None, None)
@@ -118,7 +118,7 @@ class ExternalSorterSuite extends FunSuite with LocalSparkContext {
     val iter = sorter.partitionedIterator.map(p => (p._1, p._2.toList))
     assert(iter.next() === (0, Nil))
     assert(iter.next() === (1, List((1, 1))))
-    assert(iter.next() === (2, (0 until 50000).map(x => (2, 2)).toList))
+    assert(iter.next() === (2, (0 until 100000).map(x => (2, 2)).toList))
     assert(iter.next() === (3, Nil))
     assert(iter.next() === (4, Nil))
     assert(iter.next() === (5, List((5, 5))))