diff --git a/src/main/php/xp/compiler/CompileRunner.class.php b/src/main/php/xp/compiler/CompileRunner.class.php
index b776a8fb..88563d1b 100755
--- a/src/main/php/xp/compiler/CompileRunner.class.php
+++ b/src/main/php/xp/compiler/CompileRunner.class.php
@@ -69,6 +69,7 @@ public static function main(array $args) {
     $in= $out= '-';
     $quiet= false;
     $augment= [];
+    $ext= \xp::CLASS_FILE_EXT;
     for ($i= 0; $i < sizeof($args); $i++) {
       if ('-t' === $args[$i]) {
         $target= $args[++$i];
@@ -78,6 +79,8 @@ public static function main(array $args) {
         $out= $args[++$i];
         $in= array_slice($args, $i + 1);
         break;
+      } else if ('-e' === $args[$i]) {
+        $ext= $args[++$i];
       } else if ('-n' === $args[$i]) {
         $out= null;
         $in= array_slice($args, $i + 1);
@@ -98,7 +101,7 @@ public static function main(array $args) {
     }
 
     $input= Input::newInstance($in);
-    $output= Output::newInstance($out);
+    $output= Output::newInstance($out)->using($ext);
 
     $t= new Timer();
     $total= $errors= 0;
diff --git a/src/main/php/xp/compiler/Output.class.php b/src/main/php/xp/compiler/Output.class.php
index 82be96d8..75b8837d 100755
--- a/src/main/php/xp/compiler/Output.class.php
+++ b/src/main/php/xp/compiler/Output.class.php
@@ -3,6 +3,7 @@
 use util\cmd\Console;
 
 abstract class Output {
+  protected $extension= \xp::CLASS_FILE_EXT;
 
   /**
    * Returns output from the command line argument
@@ -24,6 +25,17 @@ public static function newInstance($arg) {
     }
   }
 
+  /**
+   * Change file extension, which defaults to `xp::CLASS_FILE_EXT`.
+   *
+   * @param  string $extension
+   * @return self
+   */
+  public function using($extension) {
+    $this->extension= '.' === $extension[0] ? $extension : '.'.$extension;
+    return $this;
+  }
+
   /**
    * Returns the target for a given input 
    *
diff --git a/src/main/php/xp/compiler/ToArchive.class.php b/src/main/php/xp/compiler/ToArchive.class.php
index 6c10a558..91a3a65a 100755
--- a/src/main/php/xp/compiler/ToArchive.class.php
+++ b/src/main/php/xp/compiler/ToArchive.class.php
@@ -21,15 +21,21 @@ public function __construct($file) {
    * @return io.streams.OutputStream
    */
   public function target($name) {
-    return new class($this->archive, $name) implements OutputStream {
-      private static $replace= [DIRECTORY_SEPARATOR => '/', '.php' => \xp::CLASS_FILE_EXT];
+    return new class($this->archive, $name, $this->extension) implements OutputStream {
+      private $archive, $name, $replace;
       private $bytes= '';
-      private $archive, $name;
 
-      public function __construct($archive, $name) { $this->archive= $archive; $this->name= $name; }
+      public function __construct($archive, $name, $extension) {
+        $this->archive= $archive;
+        $this->name= $name;
+        $this->replace= [DIRECTORY_SEPARATOR => '/', '.php' => $extension];
+      }
+
       public function write($bytes) { $this->bytes.= $bytes; }
+
       public function flush() {  }
-      public function close() { $this->archive->addBytes(strtr($this->name, self::$replace), $this->bytes); }
+
+      public function close() { $this->archive->addBytes(strtr($this->name, $this->replace), $this->bytes); }
     };
   }
 
diff --git a/src/main/php/xp/compiler/ToFolder.class.php b/src/main/php/xp/compiler/ToFolder.class.php
index c1f11256..56773dd2 100755
--- a/src/main/php/xp/compiler/ToFolder.class.php
+++ b/src/main/php/xp/compiler/ToFolder.class.php
@@ -18,9 +18,9 @@ public function __construct($folder) {
    */
   public function target($name) {
     if ('-' === $name) {
-      $f= new File($this->folder, 'out'.\xp::CLASS_FILE_EXT);
+      $f= new File($this->folder, 'out'.$this->extension);
     } else {
-      $f= new File($this->folder, str_replace('.php', \xp::CLASS_FILE_EXT, $name));
+      $f= new File($this->folder, str_replace('.php', $this->extension, $name));
     }
     $this->ensure($f->path);
     return $f->out();
diff --git a/src/test/php/lang/ast/unittest/cli/ToFolderTest.class.php b/src/test/php/lang/ast/unittest/cli/ToFolderTest.class.php
index b3fe466c..8b054314 100755
--- a/src/test/php/lang/ast/unittest/cli/ToFolderTest.class.php
+++ b/src/test/php/lang/ast/unittest/cli/ToFolderTest.class.php
@@ -28,10 +28,10 @@ public function can_create() {
 
   #[Test]
   public function dash_special_case() {
-    with ((new ToFolder($this->folder))->target('-'), function($out) {
+    with ((new ToFolder($this->folder))->using('.php')->target('-'), function($out) {
       $out->write('<?php ...');
     });
-    Assert::true((new File($this->folder, 'out'.\xp::CLASS_FILE_EXT))->exists());
+    Assert::true((new File($this->folder, 'out.php'))->exists());
   }
 
   #[Test]