diff --git a/src/Composer/DependencyResolver/RuleSet.php b/src/Composer/DependencyResolver/RuleSet.php
index f7dd1c446..6d79a9678 100644
--- a/src/Composer/DependencyResolver/RuleSet.php
+++ b/src/Composer/DependencyResolver/RuleSet.php
@@ -55,7 +55,7 @@ class RuleSet implements \IteratorAggregate, \Countable
     public function add(Rule $rule, $type)
     {
         if (!isset(self::$types[$type])) {
-            throw OutOfBoundsException('Unknown rule type: ' . $type);
+            throw new \OutOfBoundsException('Unknown rule type: ' . $type);
         }
 
         if (!isset($this->rules[$type])) {
diff --git a/src/Composer/DependencyResolver/RuleSetIterator.php b/src/Composer/DependencyResolver/RuleSetIterator.php
index 46abb8ac7..63563ae51 100644
--- a/src/Composer/DependencyResolver/RuleSetIterator.php
+++ b/src/Composer/DependencyResolver/RuleSetIterator.php
@@ -88,6 +88,7 @@ class RuleSetIterator implements \Iterator
 
     public function valid()
     {
-        return isset($this->rules[$this->currentType][$this->currentOffset]);
+        return isset($this->rules[$this->currentType])
+               && isset($this->rules[$this->currentType][$this->currentOffset]);
     }
 }