diff --git a/core/src/main/scala/spark/rdd/IndexedRDD.scala b/core/src/main/scala/spark/rdd/IndexedRDD.scala
index b65efa4447..7d8e0d3938 100644
--- a/core/src/main/scala/spark/rdd/IndexedRDD.scala
+++ b/core/src/main/scala/spark/rdd/IndexedRDD.scala
@@ -350,15 +350,12 @@ class IndexedRDD[K: ClassManifest, V: ClassManifest](
             // Get the corresponding indicies and values for this IndexedRDD
             val (thisIndex, thisValues) = thisTuplesIter.next()
             assert(!thisTuplesIter.hasNext())
-            assert(thisIndex.size == thisValues.size)
             // Construct a new index
             val newIndex = thisIndex.clone().asInstanceOf[JHashMap[K, Int]]
-            assert(thisIndex.size == newIndex.size)
             // Construct a new array Buffer to store the values
             val newValues = ArrayBuffer.fill[(Seq[V], ArrayBuffer[W])](thisValues.size)(null)
             // populate the newValues with the values in this IndexedRDD
             for ((k,i) <- thisIndex) {
-              assert(i < thisValues.size)
               if (thisValues(i) != null) {
                 newValues(i) = (thisValues(i), ArrayBuffer.empty[W]) 
               }
@@ -619,7 +616,10 @@ object IndexedRDD {
           assert(!indexIter.hasNext())
           val values = new Array[Seq[V]](index.size)
           for ((k,v) <- tblIter) {
-            assert(index.contains(k))
+            if (!index.contains(k)) {
+              throw new SparkException("Error: Try to bind an external index " +
+                "to an RDD which contains keys that are not in the index.")
+            }
             val ind = index(k)
             if (values(ind) == null) {
               values(ind) = ArrayBuffer.empty[V]