diff --git a/core/Object.php b/core/Object.php
index d2cf878dc..56ee9cac4 100755
--- a/core/Object.php
+++ b/core/Object.php
@@ -970,7 +970,7 @@ abstract class Object {
 
 		if(!empty($this->beforeExtendCallbacks[$method])) {
 			foreach(array_reverse($this->beforeExtendCallbacks[$method]) as $callback) {
-				$value = call_user_func($callback, $a1, $a2, $a3, $a4, $a5, $a6, $a7);
+				$value = call_user_func_array($callback, array(&$a1, &$a2, &$a3, &$a4, &$a5, &$a6, &$a7));
 				if($value !== null) $values[] = $value;
 			}
 			$this->beforeExtendCallbacks[$method] = array();
@@ -987,7 +987,7 @@ abstract class Object {
 
 		if(!empty($this->afterExtendCallbacks[$method])) {
 			foreach(array_reverse($this->afterExtendCallbacks[$method]) as $callback) {
-				$value = call_user_func($callback, $a1, $a2, $a3, $a4, $a5, $a6, $a7);
+				$value = call_user_func_array($callback, array(&$a1, &$a2, &$a3, &$a4, &$a5, &$a6, &$a7));
 				if($value !== null) $values[] = $value;
 			}
 			$this->afterExtendCallbacks[$method] = array();
diff --git a/tests/core/ObjectTest.php b/tests/core/ObjectTest.php
index d4ee89969..487affb97 100644
--- a/tests/core/ObjectTest.php
+++ b/tests/core/ObjectTest.php
@@ -383,6 +383,19 @@ class ObjectTest extends SapphireTest {
 			$object->invokeWithExtensions('extendableMethod', 'test'),
 			array('ExtendTest(test)', 'ExtendTest2(modified)')
 		);
+
+		$object2 = new ObjectTest_Extending();
+		$first = 1;
+		$second = 2;
+		$third = 3;
+		$result = $object2->getResults($first, $second, $third);
+		$this->assertEquals(
+			array(array('before', 'extension', 'after')),
+			$result
+		);
+		$this->assertEquals(31, $first);
+		$this->assertEquals(32, $second);
+		$this->assertEquals(33, $third);
 	}
 
 	public function testParseClassSpec() {
@@ -600,4 +613,52 @@ class ObjectTest_ExtendTest4 extends ObjectTest_ExtendTest3 {
 	public function extendableMethod($argument = null) { return "ExtendTest4($argument)"; }
 }
 
+class ObjectTest_Extending extends Object implements TestOnly {
+
+	private static $extensions = array(
+		'ObjectTest_Extending_Extension'
+	);
+
+	public function getResults(&$first, &$second, &$third) {
+		// Before extending should be invoked second
+		$this->beforeExtending('updateResult', function(&$first, &$second, &$third) {
+			if($first === 1 && $second === 2 && $third === 3) {
+				$first = 11;
+				$second = 12;
+				$third = 13;
+				return 'before';
+			}
+			return 'before-error';
+		});
+
+		// After extending should be invoked fourth
+		$this->afterExtending('updateResult', function(&$first, &$second, &$third) {
+			if($first === 21 && $second === 22 && $third = 23) {
+				$first = 31;
+				$second = 32;
+				$third = 33;
+				return 'after';
+			}
+			return 'after-error';
+		});
+
+		// Function body invoked first
+		$result = $this->extend('updateResult', $first, $second, $third);
+		return array($result);
+	}
+}
+
+class ObjectTest_Extending_Extension extends Extension implements TestOnly {
+	public function updateResult(&$first, &$second, &$third) {
+		// Extension should be invoked third
+		if($first === 11 && $second === 12 && $third == 13) {
+			$first = 21;
+			$second = 22;
+			$third = 23;
+			return 'extension';
+		}
+		return 'extension-error';
+	}
+}
+
 /**#@-*/