diff --git a/build.xml b/build.xml
index 11a03ed0788..c6c2c843ac5 100644
--- a/build.xml
+++ b/build.xml
@@ -331,6 +331,20 @@
             <arg value="${type}"/>
         </exec>
 
+        <exec executable="${basedir}/build/tools/php-scoper" taskname="php-scoper">
+            <arg value="add-prefix" />
+            <arg value="--no-ansi" />
+            <arg value="--config" />
+            <arg path="${basedir}/build/scoper.inc.php" />
+            <arg value="--no-interaction" />
+            <arg value="--stop-on-failure" />
+            <arg value="--output-dir" />
+            <arg path="${basedir}/build/phar-prefixed" />
+            <arg value="--prefix" />
+            <arg value="PHPUnit" />
+            <arg path="${basedir}/build/phar" />
+        </exec>
+
         <exec executable="${basedir}/build/tools/phpab" taskname="phpab" failonerror="true">
             <arg value="--all" />
             <arg value="--static" />
@@ -359,12 +373,13 @@
             <arg path="${basedir}/build/phpunit-${_version}.phar" />
             <arg value="--template" />
             <arg path="${basedir}/build/binary-phar-autoload.php" />
-            <arg path="${basedir}/build/phar" />
+            <arg path="${basedir}/build/phar-prefixed" />
         </exec>
 
         <chmod file="${basedir}/build/phpunit-${_version}.phar" perm="ugo+rx"/>
 
         <delete dir="${basedir}/build/phar"/>
+
         <delete file="${basedir}/build/binary-phar-autoload.php"/>
     </target>
 
diff --git a/build/scoper.inc.php b/build/scoper.inc.php
new file mode 100644
index 00000000000..2452530dc8a
--- /dev/null
+++ b/build/scoper.inc.php
@@ -0,0 +1,24 @@
+<?php
+declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+$whitelistClasses = [
+    'PHPUnit\PHPUnit\Exception',
+    'PHPUnit\SoapClient',
+    'PHPUnit\Framework\*',
+    'PHPUnit_Framework_MockObject_MockObject',
+    'SebastianBergmann\CodeCoverage\*',
+    'PharIo\*',
+    'PHP_Token*',
+];
+
+return [
+    'whitelist' => $whitelistClasses,
+];
diff --git a/build/tools/php-scoper b/build/tools/php-scoper
new file mode 100644
index 00000000000..0ce73af5bec
Binary files /dev/null and b/build/tools/php-scoper differ
diff --git a/build/tools/php-scoper.pubkey b/build/tools/php-scoper.pubkey
new file mode 100644
index 00000000000..a1455c67935
--- /dev/null
+++ b/build/tools/php-scoper.pubkey
@@ -0,0 +1,14 @@
+-----BEGIN PUBLIC KEY-----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+-----END PUBLIC KEY-----