diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
index 2d2b3847dec61ee4cf97e68a6585ec462a026492..d0ca289a6ce1dd92fdecf936182521f22fc8568a 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
@@ -584,9 +584,11 @@ class JavaPairRDD[K, V](val rdd: RDD[(K, V)])(implicit val kManifest: ClassManif
    * order of the keys).
    */
   def sortByKey(comp: Comparator[K], ascending: Boolean): JavaPairRDD[K, V] = {
-    // numPartitions should never be negative in practice so we can use -1 here to indicate that
-    // we want to use implementation's default value.
-    sortByKey(comp, ascending, -1)
+    class KeyOrdering(val a: K) extends Ordered[K] {
+      override def compare(b: K) = comp.compare(a, b)
+    }
+    implicit def toOrdered(x: K): Ordered[K] = new KeyOrdering(x)
+    fromRDD(new OrderedRDDFunctions[K, V, (K, V)](rdd).sortByKey(ascending))
   }
 
   /**
@@ -600,11 +602,7 @@ class JavaPairRDD[K, V](val rdd: RDD[(K, V)])(implicit val kManifest: ClassManif
       override def compare(b: K) = comp.compare(a, b)
     }
     implicit def toOrdered(x: K): Ordered[K] = new KeyOrdering(x)
-    if (numPartitions < 0) {
-      fromRDD(new OrderedRDDFunctions[K, V, (K, V)](rdd).sortByKey(ascending))
-    } else {
-      fromRDD(new OrderedRDDFunctions[K, V, (K, V)](rdd).sortByKey(ascending, numPartitions))
-    }
+    fromRDD(new OrderedRDDFunctions[K, V, (K, V)](rdd).sortByKey(ascending, numPartitions))
   }
 
   /**