diff --git a/bin/box b/bin/box
index 2b59c6950..df8e361c3 100755
--- a/bin/box
+++ b/bin/box
@@ -53,7 +53,7 @@ $findPhpScoperFunctions = function () {
     throw new RuntimeException('Unable to find the PHP-Scoper functions.');
 };
 
-$bootstrap = function () use ($findAutoloader, $findPhpScoperFunctions) {
+$bootstrap = function () use ($findAutoloader, $findPhpScoperFunctions): void {
     require_once $findAutoloader();
     require_once $findPhpScoperFunctions();
 };
diff --git a/doc/configuration.md b/doc/configuration.md
index be49fc73e..543f9dae3 100644
--- a/doc/configuration.md
+++ b/doc/configuration.md
@@ -206,7 +206,7 @@ The default PHAR stub file can be used but Box also propose a couple of options
 
 The stub (`string`|`boolean`) setting is used to specify the location of a stub file or if one should be generated:
 - `string`: Path to the stub file will be used as is inside the PHAR
-- `true`: A new stub will be generated
+- `true` (default): A new stub will be generated
 - `false`: The default stub used by the PHAR class will be used
 
 If a custom stub file is provided, none of the other options ([`shebang`][shebang], [`intercept`][intercept] and
@@ -239,7 +239,8 @@ The `alias` (`string`) setting is used when generating a new stub to call the [`
 makes it easier to refer to files in the PHAR and ensure the access to internal files will always work regardless of the
 location of the PHAR on the file system.
 
-No alias is used by default.
+If no alias is provided, a generated unique name will be used for it in order to map the [main file][main]. Note that this
+may have undesirable effects if you are using the generated [stub][stub-stub]
 
 Example:
 
diff --git a/src/Box.php b/src/Box.php
index 3251ec446..b28390a67 100644
--- a/src/Box.php
+++ b/src/Box.php
@@ -331,7 +331,7 @@ private function processContents(array $files, string $cwd): array
         $mapFile = $this->mapFile;
         $placeholders = $this->placeholders;
         $compactors = $this->compactors;
-        $bootstrap = $GLOBALS['bootstrap'] ?? function () {};
+        $bootstrap = $GLOBALS['bootstrap'] ?? function (): void {};
 
         $processFile = function (string $file) use ($cwd, $basePath, $mapFile, $placeholders, $compactors, $bootstrap): array {
             chdir($cwd);
diff --git a/src/Configuration.php b/src/Configuration.php
index 6d20239ce..66f25837d 100644
--- a/src/Configuration.php
+++ b/src/Configuration.php
@@ -37,6 +37,7 @@
 use function KevinGH\Box\FileSystem\longest_common_base_path;
 use function KevinGH\Box\FileSystem\make_path_absolute;
 use function KevinGH\Box\FileSystem\make_path_relative;
+use function uniqid;
 
 final class Configuration
 {
@@ -115,7 +116,7 @@ final class Configuration
      */
     private function __construct(
         ?string $file,
-        ?string $alias,
+        string $alias,
         string $basePath,
         array $files,
         array $binaryFiles,
@@ -271,7 +272,7 @@ public static function create(?string $file, stdClass $raw): self
         );
     }
 
-    public function getAlias(): ?string
+    public function getAlias(): string
     {
         return $this->alias;
     }
@@ -411,10 +412,10 @@ public function isStubGenerated(): bool
         return $this->isStubGenerated;
     }
 
-    private static function retrieveAlias(stdClass $raw): ?string
+    private static function retrieveAlias(stdClass $raw): string
     {
         if (false === isset($raw->alias)) {
-            return null;
+            return uniqid('box-auto-generated-alias-').'.phar';
         }
 
         $alias = trim($raw->alias);
diff --git a/src/Console/Command/Compile.php b/src/Console/Command/Compile.php
index 77fdfcd84..a474f54c9 100644
--- a/src/Console/Command/Compile.php
+++ b/src/Console/Command/Compile.php
@@ -349,17 +349,15 @@ private function registerStub(Configuration $config, Box $box, string $main, Bui
 
             $box->registerStub($stub);
         } else {
-            if (null !== $config->getAlias()) {
-                $aliasWasAdded = $box->getPhar()->setAlias($config->getAlias());
+            $aliasWasAdded = $box->getPhar()->setAlias($config->getAlias());
 
-                Assertion::true(
-                    $aliasWasAdded,
-                    sprintf(
-                        'The alias "%s" is invalid. See Phar::setAlias() documentation for more information.',
-                        $config->getAlias()
-                    )
-                );
-            }
+            Assertion::true(
+                $aliasWasAdded,
+                sprintf(
+                    'The alias "%s" is invalid. See Phar::setAlias() documentation for more information.',
+                    $config->getAlias()
+                )
+            );
 
             $box->getPhar()->setDefaultStub($main);
 
diff --git a/src/StubGenerator.php b/src/StubGenerator.php
index 4fe5ac8ec..9fb51e5ce 100644
--- a/src/StubGenerator.php
+++ b/src/StubGenerator.php
@@ -189,7 +189,10 @@ private function generatePharConfigStmt(): ?string
         }
 
         if (null !== $this->index) {
-            $stub[] = "require 'phar://' . __FILE__ . '/{$this->index}';";
+            $stub[] = null === $this->alias
+                ? "require 'phar://' . __FILE__ . '/{$this->index}';"
+                : "require 'phar://{$this->alias}/{$this->index}';"
+            ;
         }
 
         if ([] === $stub) {
diff --git a/tests/ConfigurationTest.php b/tests/ConfigurationTest.php
index 3c28e83e8..dc874b330 100644
--- a/tests/ConfigurationTest.php
+++ b/tests/ConfigurationTest.php
@@ -70,10 +70,10 @@ public function test_it_can_be_created_without_a_file(): void
         $this->assertTrue(true);
     }
 
-    public function test_no_alias_is_registered_by_default(): void
+    public function test_a_default_alias_is_generted_if_no_alias_is_registered(): void
     {
-        $this->assertNull($this->config->getAlias());
-        $this->assertNull($this->getNoFileConfig()->getAlias());
+        $this->assertRegExp('/^box-auto-generated-alias-[\da-zA-Z]{13}\.phar$/', $this->config->getAlias());
+        $this->assertRegExp('/^box-auto-generated-alias-[\da-zA-Z]{13}\.phar$/', $this->getNoFileConfig()->getAlias());
     }
 
     public function test_the_alias_can_be_configured(): void
diff --git a/tests/Console/Command/CompileTest.php b/tests/Console/Command/CompileTest.php
index 6107ee0c7..65d1c4d75 100644
--- a/tests/Console/Command/CompileTest.php
+++ b/tests/Console/Command/CompileTest.php
@@ -29,6 +29,7 @@
 use Traversable;
 use function KevinGH\Box\FileSystem\mirror;
 use function KevinGH\Box\FileSystem\rename;
+use function preg_replace;
 
 /**
  * @covers \KevinGH\Box\Console\Command\Compile
@@ -147,7 +148,7 @@ public function test_it_can_build_a_PHAR_file(): void
  */
 
 Phar::mapPhar('alias-test.phar');
-require 'phar://' . __FILE__ . '/run.php';
+require 'phar://alias-test.phar/run.php';
 
 __HALT_COMPILER(); ?>
 
@@ -332,8 +333,6 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
                     'files' => ['test.php'],
                     'finder' => [['in' => 'one']],
                     'finder-bin' => [['in' => 'two']],
-                    'key' => 'private.key',
-                    'key-pass' => true,
                     'main' => 'run.php',
                     'map' => [
                         ['a/deep/test/directory' => 'sub'],
@@ -348,7 +347,6 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
 
         $commandTester = $this->getCommandTester();
 
-        $commandTester->setInputs(['test']);    // Set input for the passphrase
         $commandTester->execute(
             ['command' => 'compile'],
             ['interactive' => true]
@@ -392,8 +390,6 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
   'rand' => $rand,
 )
 ? No compression
-? Signing using a private key
-Private key passphrase:
 ? Setting file permissions to 493
 * Done.
 
@@ -413,6 +409,12 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
             'Expected PHAR to be executable'
         );
 
+        $this->assertSame(
+            'Hello, world!',
+            exec('cp test.phar test; php test'),
+            'Expected PHAR can be renamed'
+        );
+
         $phar = new Phar('test.phar');
 
         // Check PHAR content
@@ -428,7 +430,7 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
  */
 
 Phar::mapPhar('alias-test.phar');
-require 'phar://' . __FILE__ . '/other/run.php';
+require 'phar://alias-test.phar/other/run.php';
 
 __HALT_COMPILER(); ?>
 
@@ -459,6 +461,80 @@ public function test_it_can_build_a_PHAR_with_complete_mapping(): void
         $this->assertSame($expectedFiles, $actualFiles);
     }
 
+    public function test_it_can_build_a_PHAR_with_complete_mapping_without_an_alias(): void
+    {
+        mirror(self::FIXTURES_DIR.'/dir000', $this->tmp);
+
+        file_put_contents(
+            'box.json',
+            json_encode(
+                [
+                    'chmod' => '0755',
+                    'compactors' => [Php::class],
+                    'directories' => ['a'],
+                    'files' => ['test.php'],
+                    'finder' => [['in' => 'one']],
+                    'finder-bin' => [['in' => 'two']],
+                    'main' => 'run.php',
+                    'map' => [
+                        ['a/deep/test/directory' => 'sub'],
+                        ['' => 'other/'],
+                    ],
+                    'metadata' => ['rand' => $rand = random_int(0, mt_getrandmax())],
+                    'output' => 'test.phar',
+                    'stub' => true,
+                ]
+            )
+        );
+
+        $commandTester = $this->getCommandTester();
+
+        $commandTester->execute(
+            ['command' => 'compile'],
+            ['interactive' => true]
+        );
+
+        $this->assertSame(
+            'Hello, world!',
+            exec('php test.phar'),
+            'Expected PHAR to be executable'
+        );
+
+        $this->assertSame(
+            'Hello, world!',
+            exec('cp test.phar test; php test'),
+            'Expected PHAR can be renamed'
+        );
+
+        $phar = new Phar('test.phar');
+
+        // Check PHAR content
+        $actualStub = preg_replace(
+            '/box-auto-generated-alias-[\da-zA-Z]{13}\.phar/',
+            'box-auto-generated-alias-__uniqid__.phar',
+            $this->normalizeDisplay($phar->getStub())
+        );
+
+        $expectedStub = <<<'PHP'
+#!/usr/bin/env php
+<?php
+
+/*
+ * Generated by Humbug Box.
+ *
+ * @link https://github.com/humbug/box
+ */
+
+Phar::mapPhar('box-auto-generated-alias-__uniqid__.phar');
+require 'phar://box-auto-generated-alias-__uniqid__.phar/other/run.php';
+
+__HALT_COMPILER(); ?>
+
+PHP;
+
+        $this->assertSame($expectedStub, $actualStub);
+    }
+
     public function test_it_can_build_a_PHAR_file_in_verbose_mode(): void
     {
         mirror(self::FIXTURES_DIR.'/dir000', $this->tmp);
diff --git a/tests/StubGeneratorTest.php b/tests/StubGeneratorTest.php
index 04b95112e..0166da5b0 100644
--- a/tests/StubGeneratorTest.php
+++ b/tests/StubGeneratorTest.php
@@ -218,7 +218,7 @@ public function test_it_can_generate_a_complete_stub(): void
 
 Phar::mapPhar('test.phar');
 Phar::interceptFileFuncs();
-require 'phar://' . __FILE__ . '/index.php';
+require 'phar://test.phar/index.php';
 
 __HALT_COMPILER(); ?>