diff --git a/core/src/main/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMap.scala b/core/src/main/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMap.scala
index ee1b168028b4ac11a6a0f43346742a7cc6e91542..d6a3cdb405cbc695623f4abfb1476543a85392be 100644
--- a/core/src/main/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMap.scala
+++ b/core/src/main/scala/org/apache/spark/util/collection/PrimitiveKeyOpenHashMap.scala
@@ -35,8 +35,15 @@ class PrimitiveKeyOpenHashMap[@specialized(Long, Int) K: ClassManifest,
   /**
    * Allocate an OpenHashMap with a fixed initial capacity
    */
-  def this(initialCapacity: Int = 64) =
+  def this(initialCapacity: Int) =
     this(new OpenHashSet[K](initialCapacity), new Array[V](initialCapacity))
+    
+  /**
+   * Allocate an OpenHashMap with a default initial capacity, providing a true
+   * no-argument constructor.
+   */
+  def this() = this(64)
+
 
   /**
    * Allocate an OpenHashMap with a fixed initial capacity