diff --git a/src/Symfony/Component/Form/CollectionField.php b/src/Symfony/Component/Form/CollectionField.php
index f982bd64abd7..70095b9d18e4 100644
--- a/src/Symfony/Component/Form/CollectionField.php
+++ b/src/Symfony/Component/Form/CollectionField.php
@@ -55,8 +55,10 @@ public function setData($collection)
             throw new UnexpectedTypeException('The data must be an array');
         }
 
-        foreach ($collection as $name => $value) {
-            $this->add($this->newField($name, $name));
+        foreach ($this as $name => $field) {
+            if (!$this->getOption('modifiable') || $name != '$$key$$') {
+                $this->remove($name);
+            }
         }
 
         parent::setData($collection);
diff --git a/tests/Symfony/Tests/Component/Form/CollectionFieldTest.php b/tests/Symfony/Tests/Component/Form/CollectionFieldTest.php
index 91fde3b682be..9a01a4d594ee 100644
--- a/tests/Symfony/Tests/Component/Form/CollectionFieldTest.php
+++ b/tests/Symfony/Tests/Component/Form/CollectionFieldTest.php
@@ -27,6 +27,31 @@ public function testSetDataAdjustsSize()
         $this->assertEquals(2, count($field));
         $this->assertEquals('foo@foo.com', $field[0]->getData());
         $this->assertEquals('foo@bar.com', $field[1]->getData());
+
+        $field->setData(array('foo@baz.com'));
+        $this->assertTrue($field[0] instanceof TestField);
+        $this->assertFalse(isset($field[1]));
+        $this->assertEquals(1, count($field));
+        $this->assertEquals('foo@baz.com', $field[0]->getData());
+    }
+
+    public function testSetDataAdjustsSizeIfModifiable()
+    {
+        $field = new CollectionField(new TestField('emails'), array(
+            'modifiable' => true,
+        ));
+        $field->setData(array('foo@foo.com', 'foo@bar.com'));
+
+        $this->assertTrue($field[0] instanceof TestField);
+        $this->assertTrue($field[1] instanceof TestField);
+        $this->assertTrue($field['$$key$$'] instanceof TestField);
+        $this->assertEquals(3, count($field));
+
+        $field->setData(array('foo@baz.com'));
+        $this->assertTrue($field[0] instanceof TestField);
+        $this->assertFalse(isset($field[1]));
+        $this->assertTrue($field['$$key$$'] instanceof TestField);
+        $this->assertEquals(2, count($field));
     }
 
     public function testThrowsExceptionIfObjectIsNotTraversable()