diff --git a/src/Symfony/Component/VarDumper/Caster/ClassStub.php b/src/Symfony/Component/VarDumper/Caster/ClassStub.php
index 9eebae082962..44b54607024f 100644
--- a/src/Symfony/Component/VarDumper/Caster/ClassStub.php
+++ b/src/Symfony/Component/VarDumper/Caster/ClassStub.php
@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\VarDumper\Caster;
 
+use Symfony\Component\VarDumper\Cloner\Stub;
+
 /**
  * Represents a PHP class identifier.
  *
@@ -58,6 +60,20 @@ public function __construct(string $identifier, $callable = null)
                     $r = new \ReflectionClass($r[0]);
                 }
             }
+
+            if (null !== $callable && $r instanceof \ReflectionFunctionAbstract) {
+                $s = ReflectionCaster::castFunctionAbstract($r, array(), new Stub(), true);
+                $s = ReflectionCaster::getSignature($s);
+
+                if ('()' === substr($identifier, -2)) {
+                    $this->value = substr_replace($identifier, $s, -2);
+                } else {
+                    $this->value .= $s;
+                }
+                if (isset($this->attr['ellipsis'])) {
+                    $this->attr['ellipsis'] += \strlen($this->value) - \strlen($identifier);
+                }
+            }
         } catch (\ReflectionException $e) {
             return;
         }
@@ -75,9 +91,9 @@ public static function wrapCallable($callable)
         }
 
         if (!is_array($callable)) {
-            $callable = new static($callable);
+            $callable = new static($callable, $callable);
         } elseif (is_string($callable[0])) {
-            $callable[0] = new static($callable[0]);
+            $callable[0] = new static($callable[0], $callable);
         } else {
             $callable[1] = new static($callable[1], $callable);
         }
diff --git a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
index b7aee3212494..7e5f3491106a 100644
--- a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
@@ -38,6 +38,8 @@ public static function castClosure(\Closure $c, array $a, Stub $stub, $isNested,
 
         $a = static::castFunctionAbstract($c, $a, $stub, $isNested, $filter);
 
+        $stub->class .= self::getSignature($a);
+
         if (isset($a[$prefix.'parameters'])) {
             foreach ($a[$prefix.'parameters']->value as &$v) {
                 $param = $v;
@@ -294,6 +296,52 @@ public static function castZendExtension(\ReflectionZendExtension $c, array $a,
         return $a;
     }
 
+    public static function getSignature(array $a)
+    {
+        $prefix = Caster::PREFIX_VIRTUAL;
+        $signature = '';
+
+        if (isset($a[$prefix.'parameters'])) {
+            foreach ($a[$prefix.'parameters']->value as $k => $param) {
+                $signature .= ', ';
+                if ($type = $param->getType()) {
+                    if (!$param->isOptional() && $param->allowsNull()) {
+                        $signature .= '?';
+                    }
+                    $signature .= substr(strrchr('\\'.$type->getName(), '\\'), 1).' ';
+                }
+                $signature .= $k;
+
+                if (!$param->isDefaultValueAvailable()) {
+                    continue;
+                }
+                $v = $param->getDefaultValue();
+                $signature .= ' = ';
+
+                if ($param->isDefaultValueConstant()) {
+                    $signature .= substr(strrchr('\\'.$param->getDefaultValueConstantName(), '\\'), 1);
+                } elseif (null === $v) {
+                    $signature .= 'null';
+                } elseif (\is_array($v)) {
+                    $signature .= $v ? '[…'.\count($v).']' : '[]';
+                } elseif (\is_string($v)) {
+                    $signature .= 10 > \strlen($v) && false === strpos($v, '\\') ? "'{$v}'" : "'…".\strlen($v)."'";
+                } elseif (\is_bool($v)) {
+                    $signature .= $v ? 'true' : 'false';
+                } else {
+                    $signature .= $v;
+                }
+            }
+        }
+        $signature = '('.substr($signature, 2).')';
+
+        if (isset($a[$prefix.'returnType'])) {
+            $signature .= ': '.substr(strrchr('\\'.$a[$prefix.'returnType'], '\\'), 1);
+        }
+
+        return $signature;
+    }
+
     private static function addExtra(&$a, \Reflector $c)
     {
         $x = isset($a[Caster::PREFIX_VIRTUAL.'extra']) ? $a[Caster::PREFIX_VIRTUAL.'extra']->value : array();
diff --git a/src/Symfony/Component/VarDumper/Tests/Caster/ReflectionCasterTest.php b/src/Symfony/Component/VarDumper/Tests/Caster/ReflectionCasterTest.php
index 3eaf958d8f68..a52445132661 100644
--- a/src/Symfony/Component/VarDumper/Tests/Caster/ReflectionCasterTest.php
+++ b/src/Symfony/Component/VarDumper/Tests/Caster/ReflectionCasterTest.php
@@ -68,14 +68,14 @@ public function testClosureCaster()
         $var = function ($x) use ($a, &$b) {};
 
         $this->assertDumpMatchesFormat(
-            <<<EOTXT
-Closure {
+            <<<'EOTXT'
+Closure($x) {
 %Aparameters: {
-    \$x: {}
+    $x: {}
   }
   use: {
-    \$a: 123
-    \$b: & 123
+    $a: 123
+    $b: & 123
   }
   file: "%sReflectionCasterTest.php"
   line: "68 to 68"
@@ -90,7 +90,7 @@ public function testClosureCasterExcludingVerbosity()
         $var = function () {};
 
         $expectedDump = <<<EOTXT
-Closure {
+Closure() {
   class: "Symfony\Component\VarDumper\Tests\Caster\ReflectionCasterTest"
   this: Symfony\Component\VarDumper\Tests\Caster\ReflectionCasterTest { …}
 }
@@ -140,7 +140,7 @@ public function testReturnType()
 
         $this->assertDumpMatchesFormat(
             <<<EOTXT
-Closure {
+Closure(): int {
   returnType: "int"
   class: "Symfony\Component\VarDumper\Tests\Caster\ReflectionCasterTest"
   this: Symfony\Component\VarDumper\Tests\Caster\ReflectionCasterTest { …}
diff --git a/src/Symfony/Component/VarDumper/Tests/Caster/StubCasterTest.php b/src/Symfony/Component/VarDumper/Tests/Caster/StubCasterTest.php
index 36603c51cc01..c587a5444836 100644
--- a/src/Symfony/Component/VarDumper/Tests/Caster/StubCasterTest.php
+++ b/src/Symfony/Component/VarDumper/Tests/Caster/StubCasterTest.php
@@ -141,7 +141,7 @@ public function testClassStub()
 
         $expectedDump = <<<'EODUMP'
 <foo></foo><bar><span class=sf-dump-note>array:1</span> [<samp>
-  <span class=sf-dump-index>0</span> => "<a href="%sFooInterface.php:10" rel="noopener noreferrer"><span class=sf-dump-str title="5 characters">hello</span></a>"
+  <span class=sf-dump-index>0</span> => "<a href="%sFooInterface.php:10" rel="noopener noreferrer"><span class=sf-dump-str title="39 characters">hello(?stdClass $a, stdClass $b = null)</span></a>"
 </samp>]
 </bar>
 EODUMP;
diff --git a/src/Symfony/Component/VarDumper/Tests/Dumper/CliDumperTest.php b/src/Symfony/Component/VarDumper/Tests/Dumper/CliDumperTest.php
index d25f88d1669f..85b0ac05b03e 100644
--- a/src/Symfony/Component/VarDumper/Tests/Dumper/CliDumperTest.php
+++ b/src/Symfony/Component/VarDumper/Tests/Dumper/CliDumperTest.php
@@ -75,7 +75,7 @@ public function testGet()
     +foo: "foo"
     +"bar": "bar"
   }
-  "closure" => Closure {#%d
+  "closure" => Closure(\$a, PDO &\$b = null) {#%d
     class: "Symfony\Component\VarDumper\Tests\Dumper\CliDumperTest"
     this: Symfony\Component\VarDumper\Tests\Dumper\CliDumperTest {#%d …}
     parameters: {
diff --git a/src/Symfony/Component/VarDumper/Tests/Dumper/HtmlDumperTest.php b/src/Symfony/Component/VarDumper/Tests/Dumper/HtmlDumperTest.php
index ac2f8f2c30a1..b87bc2a0072c 100644
--- a/src/Symfony/Component/VarDumper/Tests/Dumper/HtmlDumperTest.php
+++ b/src/Symfony/Component/VarDumper/Tests/Dumper/HtmlDumperTest.php
@@ -78,7 +78,7 @@ public function testGet()
     +<span class=sf-dump-public title="Public property">foo</span>: "<span class=sf-dump-str title="3 characters">foo</span>"
     +"<span class=sf-dump-public title="Runtime added dynamic property">bar</span>": "<span class=sf-dump-str title="3 characters">bar</span>"
   </samp>}
-  "<span class=sf-dump-key>closure</span>" => <span class=sf-dump-note>Closure</span> {<a class=sf-dump-ref>#%d</a><samp>
+  "<span class=sf-dump-key>closure</span>" => <span class=sf-dump-note>Closure(\$a, PDO &amp;\$b = null)</span> {<a class=sf-dump-ref>#%d</a><samp>
     <span class=sf-dump-meta>class</span>: "<span class=sf-dump-str title="Symfony\Component\VarDumper\Tests\Dumper\HtmlDumperTest
 55 characters"><span class="sf-dump-ellipsis sf-dump-ellipsis-class">Symfony\Component\VarDumper\Tests\Dumper</span><span class=sf-dump-ellipsis>\</span>HtmlDumperTest</span>"
     <span class=sf-dump-meta>this</span>: <abbr title="Symfony\Component\VarDumper\Tests\Dumper\HtmlDumperTest" class=sf-dump-note>HtmlDumperTest</abbr> {<a class=sf-dump-ref>#%d</a> &%s;}
diff --git a/src/Symfony/Component/VarDumper/Tests/Fixtures/FooInterface.php b/src/Symfony/Component/VarDumper/Tests/Fixtures/FooInterface.php
index 874110a5b64f..172958b47e2a 100644
--- a/src/Symfony/Component/VarDumper/Tests/Fixtures/FooInterface.php
+++ b/src/Symfony/Component/VarDumper/Tests/Fixtures/FooInterface.php
@@ -7,5 +7,5 @@ interface FooInterface
     /**
      * Hello.
      */
-    public function foo();
+    public function foo(?\stdClass $a, \stdClass $b = null);
 }