diff --git a/lib/Twig/Environment.php b/lib/Twig/Environment.php
index 766d0a9f2..c7795dd84 100644
--- a/lib/Twig/Environment.php
+++ b/lib/Twig/Environment.php
@@ -829,7 +829,7 @@ class Twig_Environment
         return false;
     }
 
-    public function registerUndefinedFilterCallback($callable)
+    public function registerUndefinedFilterCallback(callable $callable)
     {
         $this->filterCallbacks[] = $callable;
     }
@@ -956,7 +956,7 @@ class Twig_Environment
         return false;
     }
 
-    public function registerUndefinedFunctionCallback($callable)
+    public function registerUndefinedFunctionCallback(callable $callable)
     {
         $this->functionCallbacks[] = $callable;
     }
diff --git a/lib/Twig/Extension/Core.php b/lib/Twig/Extension/Core.php
index f070e5284..01a5d5608 100644
--- a/lib/Twig/Extension/Core.php
+++ b/lib/Twig/Extension/Core.php
@@ -26,7 +26,7 @@ class Twig_Extension_Core extends Twig_Extension
      * @param string   $strategy The strategy name that should be used as a strategy in the escape call
      * @param callable $callable A valid PHP callable
      */
-    public function setEscaper($strategy, $callable)
+    public function setEscaper($strategy, callable $callable)
     {
         $this->escapers[$strategy] = $callable;
     }
@@ -34,7 +34,7 @@ class Twig_Extension_Core extends Twig_Extension
     /**
      * Gets all defined escapers.
      *
-     * @return array An array of escapers
+     * @return callable[] An array of escapers
      */
     public function getEscapers()
     {
diff --git a/lib/Twig/Filter.php b/lib/Twig/Filter.php
index 3bb2c5f1b..a984e2e34 100644
--- a/lib/Twig/Filter.php
+++ b/lib/Twig/Filter.php
@@ -13,6 +13,8 @@
  * Represents a template filter.
  *
  * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @see http://twig.sensiolabs.org/doc/templates.html#filters
  */
 class Twig_Filter
 {
@@ -21,7 +23,14 @@ class Twig_Filter
     private $options;
     private $arguments = array();
 
-    public function __construct($name, $callable, array $options = array())
+    /**
+     * Creates a template filter.
+     *
+     * @param string        $name     Name of this filter
+     * @param callable|null $callable A callable implementing the filter. If null, you need to overwrite the "node_class" option to customize compilation.
+     * @param array         $options  Options array
+     */
+    public function __construct($name, callable $callable = null, array $options = array())
     {
         $this->name = $name;
         $this->callable = $callable;
@@ -44,6 +53,11 @@ class Twig_Filter
         return $this->name;
     }
 
+    /**
+     * Returns the callable to execute for this filter.
+     *
+     * @return callable|null
+     */
     public function getCallable()
     {
         return $this->callable;
diff --git a/lib/Twig/Function.php b/lib/Twig/Function.php
index d673a2940..09ddc4cf1 100644
--- a/lib/Twig/Function.php
+++ b/lib/Twig/Function.php
@@ -13,6 +13,8 @@
  * Represents a template function.
  *
  * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @see http://twig.sensiolabs.org/doc/templates.html#functions
  */
 class Twig_Function
 {
@@ -21,7 +23,14 @@ class Twig_Function
     private $options;
     private $arguments = array();
 
-    public function __construct($name, $callable, array $options = array())
+    /**
+     * Creates a template function.
+     *
+     * @param string        $name     Name of this function
+     * @param callable|null $callable A callable implementing the function. If null, you need to overwrite the "node_class" option to customize compilation.
+     * @param array         $options  Options array
+     */
+    public function __construct($name, callable $callable = null, array $options = array())
     {
         $this->name = $name;
         $this->callable = $callable;
@@ -42,6 +51,11 @@ class Twig_Function
         return $this->name;
     }
 
+    /**
+     * Returns the callable to execute for this function.
+     *
+     * @return callable|null
+     */
     public function getCallable()
     {
         return $this->callable;
diff --git a/lib/Twig/Node/Expression/Call.php b/lib/Twig/Node/Expression/Call.php
index 20c4c3e63..f0269d121 100644
--- a/lib/Twig/Node/Expression/Call.php
+++ b/lib/Twig/Node/Expression/Call.php
@@ -19,9 +19,15 @@ abstract class Twig_Node_Expression_Call extends Twig_Node_Expression
             $compiler->raw($callable);
         } elseif (is_array($callable) && $callable[0] instanceof Twig_ExtensionInterface) {
             $compiler->raw(sprintf('$this->env->getExtension(\'%s\')->%s', $callable[0]->getName(), $callable[1]));
-        } else {
+        } elseif (null !== $callable) {
             $closingParenthesis = true;
             $compiler->raw(sprintf('call_user_func_array($this->env->get%s(\'%s\')->getCallable(), array', ucfirst($this->getAttribute('type')), $this->getAttribute('name')));
+        } else {
+            throw new LogicException(sprintf(
+                '%s "%s" cannot be compiled because it does not define a callable to execute. Maybe you want to change compilation with a custom node class.',
+                ucfirst($this->getAttribute('type')),
+                $this->getAttribute('name')
+            ));
         }
 
         $this->compileArguments($compiler);
@@ -83,7 +89,7 @@ abstract class Twig_Node_Expression_Call extends Twig_Node_Expression
         $compiler->raw(')');
     }
 
-    protected function getArguments($callable, $arguments)
+    protected function getArguments(callable $callable = null, $arguments)
     {
         $callType = $this->getAttribute('type');
         $callName = $this->getAttribute('name');
diff --git a/lib/Twig/Test.php b/lib/Twig/Test.php
index 44e109d28..a39d922d8 100644
--- a/lib/Twig/Test.php
+++ b/lib/Twig/Test.php
@@ -13,6 +13,8 @@
  * Represents a template test.
  *
  * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @see http://twig.sensiolabs.org/doc/templates.html#test-operator
  */
 class Twig_Test
 {
@@ -20,7 +22,14 @@ class Twig_Test
     private $callable;
     private $options;
 
-    public function __construct($name, $callable, array $options = array())
+    /**
+     * Creates a template test.
+     *
+     * @param string        $name     Name of this test
+     * @param callable|null $callable A callable implementing the test. If null, you need to overwrite the "node_class" option to customize compilation.
+     * @param array         $options  Options array
+     */
+    public function __construct($name, callable $callable = null, array $options = array())
     {
         $this->name = $name;
         $this->callable = $callable;
@@ -37,6 +46,11 @@ class Twig_Test
         return $this->name;
     }
 
+    /**
+     * Returns the callable to execute for this test.
+     *
+     * @return callable|null
+     */
     public function getCallable()
     {
         return $this->callable;
diff --git a/test/Twig/Tests/EnvironmentTest.php b/test/Twig/Tests/EnvironmentTest.php
index 00c32de6b..df7426c52 100644
--- a/test/Twig/Tests/EnvironmentTest.php
+++ b/test/Twig/Tests/EnvironmentTest.php
@@ -190,21 +190,21 @@ class Twig_Tests_EnvironmentTest_Extension extends Twig_Extension
     public function getFilters()
     {
         return array(
-            new Twig_Filter('foo_filter', 'foo_filter'),
+            new Twig_Filter('foo_filter'),
         );
     }
 
     public function getTests()
     {
         return array(
-            new Twig_Test('foo_test', 'foo_test'),
+            new Twig_Test('foo_test'),
         );
     }
 
     public function getFunctions()
     {
         return array(
-            new Twig_Function('foo_function', 'foo_function'),
+            new Twig_Function('foo_function'),
         );
     }
 
diff --git a/test/Twig/Tests/Node/Expression/FilterTest.php b/test/Twig/Tests/Node/Expression/FilterTest.php
index 48f929bda..0482daca3 100644
--- a/test/Twig/Tests/Node/Expression/FilterTest.php
+++ b/test/Twig/Tests/Node/Expression/FilterTest.php
@@ -26,7 +26,7 @@ class Twig_Tests_Node_Expression_FilterTest extends Twig_Test_NodeTestCase
     public function getTests()
     {
         $environment = new Twig_Environment($this->getMock('Twig_LoaderInterface'));
-        $environment->addFilter(new Twig_SimpleFilter('bar', 'bar', array('needs_environment' => true)));
+        $environment->addFilter(new Twig_SimpleFilter('bar', 'twig_tests_filter_dummy', array('needs_environment' => true)));
         $environment->addFilter(new Twig_SimpleFilter('barbar', 'twig_tests_filter_barbar', array('needs_context' => true, 'is_variadic' => true)));
 
         $tests = array();
@@ -73,10 +73,10 @@ class Twig_Tests_Node_Expression_FilterTest extends Twig_Test_NodeTestCase
 
         // needs environment
         $node = $this->createFilter($string, 'bar');
-        $tests[] = array($node, 'bar($this->env, "abc")', $environment);
+        $tests[] = array($node, 'twig_tests_filter_dummy($this->env, "abc")', $environment);
 
         $node = $this->createFilter($string, 'bar', array(new Twig_Node_Expression_Constant('bar', 1)));
-        $tests[] = array($node, 'bar($this->env, "abc", "bar")', $environment);
+        $tests[] = array($node, 'twig_tests_filter_dummy($this->env, "abc", "bar")', $environment);
 
         // arbitrary named arguments
         $node = $this->createFilter($string, 'barbar');
@@ -146,6 +146,10 @@ class Twig_Tests_Node_Expression_FilterTest extends Twig_Test_NodeTestCase
     }
 }
 
+function twig_tests_filter_dummy()
+{
+}
+
 function twig_tests_filter_barbar($context, $string, $arg1 = null, $arg2 = null, array $args = array())
 {
 }
diff --git a/test/Twig/Tests/Node/Expression/FunctionTest.php b/test/Twig/Tests/Node/Expression/FunctionTest.php
index f13c3b6c2..b0c259d67 100644
--- a/test/Twig/Tests/Node/Expression/FunctionTest.php
+++ b/test/Twig/Tests/Node/Expression/FunctionTest.php
@@ -24,37 +24,37 @@ class Twig_Tests_Node_Expression_FunctionTest extends Twig_Test_NodeTestCase
     public function getTests()
     {
         $environment = new Twig_Environment($this->getMock('Twig_LoaderInterface'));
-        $environment->addFunction(new Twig_Function('foo', 'foo', array()));
-        $environment->addFunction(new Twig_Function('bar', 'bar', array('needs_environment' => true)));
-        $environment->addFunction(new Twig_Function('foofoo', 'foofoo', array('needs_context' => true)));
-        $environment->addFunction(new Twig_Function('foobar', 'foobar', array('needs_environment' => true, 'needs_context' => true)));
+        $environment->addFunction(new Twig_Function('foo', 'twig_tests_function_dummy', array()));
+        $environment->addFunction(new Twig_Function('bar', 'twig_tests_function_dummy', array('needs_environment' => true)));
+        $environment->addFunction(new Twig_Function('foofoo', 'twig_tests_function_dummy', array('needs_context' => true)));
+        $environment->addFunction(new Twig_Function('foobar', 'twig_tests_function_dummy', array('needs_environment' => true, 'needs_context' => true)));
         $environment->addFunction(new Twig_Function('barbar', 'twig_tests_function_barbar', array('is_variadic' => true)));
 
         $tests = array();
 
         $node = $this->createFunction('foo');
-        $tests[] = array($node, 'foo()', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy()', $environment);
 
         $node = $this->createFunction('foo', array(new Twig_Node_Expression_Constant('bar', 1), new Twig_Node_Expression_Constant('foobar', 1)));
-        $tests[] = array($node, 'foo("bar", "foobar")', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy("bar", "foobar")', $environment);
 
         $node = $this->createFunction('bar');
-        $tests[] = array($node, 'bar($this->env)', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($this->env)', $environment);
 
         $node = $this->createFunction('bar', array(new Twig_Node_Expression_Constant('bar', 1)));
-        $tests[] = array($node, 'bar($this->env, "bar")', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($this->env, "bar")', $environment);
 
         $node = $this->createFunction('foofoo');
-        $tests[] = array($node, 'foofoo($context)', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($context)', $environment);
 
         $node = $this->createFunction('foofoo', array(new Twig_Node_Expression_Constant('bar', 1)));
-        $tests[] = array($node, 'foofoo($context, "bar")', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($context, "bar")', $environment);
 
         $node = $this->createFunction('foobar');
-        $tests[] = array($node, 'foobar($this->env, $context)', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($this->env, $context)', $environment);
 
         $node = $this->createFunction('foobar', array(new Twig_Node_Expression_Constant('bar', 1)));
-        $tests[] = array($node, 'foobar($this->env, $context, "bar")', $environment);
+        $tests[] = array($node, 'twig_tests_function_dummy($this->env, $context, "bar")', $environment);
 
         // named arguments
         $node = $this->createFunction('date', array(
@@ -102,6 +102,10 @@ class Twig_Tests_Node_Expression_FunctionTest extends Twig_Test_NodeTestCase
     }
 }
 
+function twig_tests_function_dummy()
+{
+}
+
 function twig_tests_function_barbar($arg1 = null, $arg2 = null, array $args = array())
 {
 }