diff --git a/ChangeLog-9.6.md b/ChangeLog-9.6.md
index bbe94625200..de708d42051 100644
--- a/ChangeLog-9.6.md
+++ b/ChangeLog-9.6.md
@@ -2,6 +2,12 @@
 
 All notable changes of the PHPUnit 9.6 release series are documented in this file using the [Keep a CHANGELOG](https://keepachangelog.com/) principles.
 
+## [9.6.13] - 2023-MM-DD
+
+### Changed
+
+* The child processes used for process isolation now use temporary files to communicate their result to the parent process
+
 ## [9.6.12] - 2023-09-12
 
 ### Changed
@@ -89,6 +95,7 @@ All notable changes of the PHPUnit 9.6 release series are documented in this fil
 * [#5064](https://github.com/sebastianbergmann/phpunit/issues/5064): Deprecate `PHPUnit\Framework\TestCase::getMockClass()`
 * [#5132](https://github.com/sebastianbergmann/phpunit/issues/5132): Deprecate `Test` suffix for abstract test case classes
 
+[9.6.13]: https://github.com/sebastianbergmann/phpunit/compare/9.6.12...9.6
 [9.6.12]: https://github.com/sebastianbergmann/phpunit/compare/9.6.11...9.6.12
 [9.6.11]: https://github.com/sebastianbergmann/phpunit/compare/9.6.10...9.6.11
 [9.6.10]: https://github.com/sebastianbergmann/phpunit/compare/9.6.9...9.6.10
diff --git a/src/Framework/TestCase.php b/src/Framework/TestCase.php
index 380759b6d17..3a67f5dd126 100644
--- a/src/Framework/TestCase.php
+++ b/src/Framework/TestCase.php
@@ -60,6 +60,8 @@
 use function sprintf;
 use function strpos;
 use function substr;
+use function sys_get_temp_dir;
+use function tempnam;
 use function trim;
 use function var_export;
 use DeepCopy\DeepCopy;
@@ -924,6 +926,7 @@ public function run(TestResult $result = null): TestResult
             $codeCoverageCacheDirectory = "'." . $codeCoverageCacheDirectory . ".'";
 
             $configurationFilePath = $GLOBALS['__PHPUNIT_CONFIGURATION_FILE'] ?? '';
+            $processResultFile     = tempnam(sys_get_temp_dir(), 'phpunit_');
 
             $var = [
                 'composerAutoload'                           => $composerAutoload,
@@ -950,6 +953,7 @@ public function run(TestResult $result = null): TestResult
                 'codeCoverageFilter'                         => $codeCoverageFilter,
                 'configurationFilePath'                      => $configurationFilePath,
                 'name'                                       => $this->getName(false),
+                'processResultFile'                          => $processResultFile,
             ];
 
             if (!$runEntireClass) {
@@ -959,7 +963,7 @@ public function run(TestResult $result = null): TestResult
             $template->setVar($var);
 
             $php = AbstractPhpProcess::factory();
-            $php->runTestJob($template->render(), $this, $result);
+            $php->runTestJob($template->render(), $this, $result, $processResultFile);
         } else {
             $result->run($this);
         }
diff --git a/src/Util/PHP/AbstractPhpProcess.php b/src/Util/PHP/AbstractPhpProcess.php
index 5b34055af23..0405d1f3350 100644
--- a/src/Util/PHP/AbstractPhpProcess.php
+++ b/src/Util/PHP/AbstractPhpProcess.php
@@ -15,6 +15,8 @@
 use function array_merge;
 use function assert;
 use function escapeshellarg;
+use function file_exists;
+use function file_get_contents;
 use function ini_get_all;
 use function restore_error_handler;
 use function set_error_handler;
@@ -24,6 +26,7 @@
 use function strrpos;
 use function substr;
 use function trim;
+use function unlink;
 use function unserialize;
 use __PHP_Incomplete_Class;
 use ErrorException;
@@ -174,16 +177,23 @@ public function getTimeout(): int
      *
      * @throws \SebastianBergmann\RecursionContext\InvalidArgumentException
      */
-    public function runTestJob(string $job, Test $test, TestResult $result): void
+    public function runTestJob(string $job, Test $test, TestResult $result, string $processResultFile): void
     {
         $result->startTest($test);
 
-        $_result = $this->runJob($job);
+        $processResult = '';
+        $_result       = $this->runJob($job);
+
+        if (file_exists($processResultFile)) {
+            $processResult = file_get_contents($processResultFile);
+
+            @unlink($processResultFile);
+        }
 
         $this->processChildResult(
             $test,
             $result,
-            $_result['stdout'],
+            $processResult,
             $_result['stderr'],
         );
     }
diff --git a/src/Util/PHP/Template/TestCaseClass.tpl b/src/Util/PHP/Template/TestCaseClass.tpl
index 95035e50521..0486d116433 100644
--- a/src/Util/PHP/Template/TestCaseClass.tpl
+++ b/src/Util/PHP/Template/TestCaseClass.tpl
@@ -58,7 +58,7 @@ function __phpunit_run_isolated_test()
 
     $test = new {className}('{name}', unserialize('{data}'), '{dataName}');
     $test->setDependencyInput(unserialize('{dependencyInput}'));
-    $test->setInIsolation(TRUE);
+    $test->setInIsolation(true);
 
     ob_end_clean();
     $test->run($result);
@@ -68,6 +68,7 @@ function __phpunit_run_isolated_test()
     }
 
     ini_set('xdebug.scream', '0');
+
     @rewind(STDOUT); /* @ as not every STDOUT target stream is rewindable */
     if ($stdout = @stream_get_contents(STDOUT)) {
         $output = $stdout . $output;
@@ -78,13 +79,16 @@ function __phpunit_run_isolated_test()
         }
     }
 
-    print serialize(
-      [
-        'testResult'    => $test->getResult(),
-        'numAssertions' => $test->getNumAssertions(),
-        'result'        => $result,
-        'output'        => $output
-      ]
+    file_put_contents(
+        '{processResultFile}',
+        serialize(
+            [
+                'testResult'    => $test->getResult(),
+                'numAssertions' => $test->getNumAssertions(),
+                'result'        => $result,
+                'output'        => $output
+            ]
+        )
     );
 }
 
diff --git a/src/Util/PHP/Template/TestCaseMethod.tpl b/src/Util/PHP/Template/TestCaseMethod.tpl
index da824e7206e..067934dbcf2 100644
--- a/src/Util/PHP/Template/TestCaseMethod.tpl
+++ b/src/Util/PHP/Template/TestCaseMethod.tpl
@@ -71,6 +71,7 @@ function __phpunit_run_isolated_test()
     }
 
     ini_set('xdebug.scream', '0');
+
     @rewind(STDOUT); /* @ as not every STDOUT target stream is rewindable */
     if ($stdout = @stream_get_contents(STDOUT)) {
         $output = $stdout . $output;
@@ -81,13 +82,16 @@ function __phpunit_run_isolated_test()
         }
     }
 
-    print serialize(
-      [
-        'testResult'    => $test->getResult(),
-        'numAssertions' => $test->getNumAssertions(),
-        'result'        => $result,
-        'output'        => $output
-      ]
+    file_put_contents(
+        '{processResultFile}',
+        serialize(
+            [
+                'testResult'    => $test->getResult(),
+                'numAssertions' => $test->getNumAssertions(),
+                'result'        => $result,
+                'output'        => $output
+            ]
+        )
     );
 }
 
diff --git a/tests/end-to-end/regression/1348.phpt b/tests/end-to-end/regression/1348.phpt
index a00913c768f..977dbb73995 100644
--- a/tests/end-to-end/regression/1348.phpt
+++ b/tests/end-to-end/regression/1348.phpt
@@ -1,11 +1,9 @@
 --TEST--
 https://github.com/sebastianbergmann/phpunit/issues/1348
---XFAIL--
-https://github.com/sebastianbergmann/phpunit/issues/5356
 --SKIPIF--
 <?php declare(strict_types=1);
-if (defined('HHVM_VERSION') || defined('PHPDBG_VERSION')) {
-    print 'skip: PHP runtime required';
+if (defined('STDOUT')) {
+    print 'skip: PHP < 8.3 required';
 }
 --FILE--
 <?php declare(strict_types=1);