diff --git a/bin/systemlib.php b/bin/systemlib.php
index ebf40507a..f2f775324 100644
--- a/bin/systemlib.php
+++ b/bin/systemlib.php
@@ -7068,7 +7068,7 @@ class RecursiveIteratorIterator implements OuterIterator, Traversable {
   public function getInnerIterator() {
     $it = $this->iterators[count($this->iterators)-1][0];
     if (!$it instanceof RecursiveDirectoryIterator) {
-      throw new NotImplementedException(
+      throw new Exception(
         "RecursiveIteratorIterator only supports RecursiveDirectoryIterator"
       );
     }
diff --git a/hphp/system/classes/spl/iterators/RecursiveIteratorIterator.php b/hphp/system/classes/spl/iterators/RecursiveIteratorIterator.php
index 880565781..e9b965d11 100644
--- a/hphp/system/classes/spl/iterators/RecursiveIteratorIterator.php
+++ b/hphp/system/classes/spl/iterators/RecursiveIteratorIterator.php
@@ -67,7 +67,7 @@ class RecursiveIteratorIterator implements OuterIterator, Traversable {
   public function getInnerIterator() {
     $it = $this->iterators[count($this->iterators)-1][0];
     if (!$it instanceof RecursiveDirectoryIterator) {
-      throw new NotImplementedException(
+      throw new Exception(
         "RecursiveIteratorIterator only supports RecursiveDirectoryIterator"
       );
     }