diff --git a/src/Symfony/Component/Process/Pipes/UnixPipes.php b/src/Symfony/Component/Process/Pipes/UnixPipes.php
index 7bd0db0e94b45..a0e48dd3634c1 100644
--- a/src/Symfony/Component/Process/Pipes/UnixPipes.php
+++ b/src/Symfony/Component/Process/Pipes/UnixPipes.php
@@ -74,7 +74,7 @@ public function getDescriptors(): array
             return [
                 ['pty'],
                 ['pty'],
-                ['pty'],
+                ['pipe', 'w'], // stderr needs to be in a pipe to correctly split error and output, since PHP will use the same stream for both
             ];
         }
 
diff --git a/src/Symfony/Component/Process/Tests/ProcessTest.php b/src/Symfony/Component/Process/Tests/ProcessTest.php
index 0f302c2aabd3c..e9c7527c42c89 100644
--- a/src/Symfony/Component/Process/Tests/ProcessTest.php
+++ b/src/Symfony/Component/Process/Tests/ProcessTest.php
@@ -540,6 +540,20 @@ public function testExitCodeTextIsNullWhenExitCodeIsNull()
         $this->assertNull($process->getExitCodeText());
     }
 
+    public function testStderrNotMixedWithStdout()
+    {
+        if (!Process::isPtySupported()) {
+            $this->markTestSkipped('PTY is not supported on this operating system.');
+        }
+
+        $process = $this->getProcess('echo "foo" && echo "bar" >&2');
+        $process->setPty(true);
+        $process->run();
+
+        $this->assertSame("foo\r\n", $process->getOutput());
+        $this->assertSame("bar\n", $process->getErrorOutput());
+    }
+
     public function testPTYCommand()
     {
         if (!Process::isPtySupported()) {