diff --git a/src/Composer/Autoload/AutoloadGenerator.php b/src/Composer/Autoload/AutoloadGenerator.php
index 71d40c116..8423fd2ad 100644
--- a/src/Composer/Autoload/AutoloadGenerator.php
+++ b/src/Composer/Autoload/AutoloadGenerator.php
@@ -741,6 +741,9 @@ EXT_CHECKS;
 \$issues = array();
 ${requiredPhp}${requiredExtensions}
 if (\$issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, \$issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/no_extensions_required.php b/tests/Composer/Test/Autoload/Fixtures/platform/no_extensions_required.php
index 762b670af..589e9e770 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/no_extensions_required.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/no_extensions_required.php
@@ -9,6 +9,9 @@ if (!(PHP_VERSION_ID >= 70200)) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/no_php_required.php b/tests/Composer/Test/Autoload/Fixtures/platform/no_php_required.php
index 0665633cd..a48283c46 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/no_php_required.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/no_php_required.php
@@ -13,6 +13,9 @@ if ($missingExtensions) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/no_php_upper_bound.php b/tests/Composer/Test/Autoload/Fixtures/platform/no_php_upper_bound.php
index 762b670af..589e9e770 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/no_php_upper_bound.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/no_php_upper_bound.php
@@ -9,6 +9,9 @@ if (!(PHP_VERSION_ID >= 70200)) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/replaced_provided_exts.php b/tests/Composer/Test/Autoload/Fixtures/platform/replaced_provided_exts.php
index 78b550268..6447885f1 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/replaced_provided_exts.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/replaced_provided_exts.php
@@ -12,6 +12,9 @@ if ($missingExtensions) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/specific_php_release.php b/tests/Composer/Test/Autoload/Fixtures/platform/specific_php_release.php
index 9ae604c1c..65492e89c 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/specific_php_release.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/specific_php_release.php
@@ -9,6 +9,9 @@ if (!(PHP_VERSION_ID >= 70208)) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);
diff --git a/tests/Composer/Test/Autoload/Fixtures/platform/typical.php b/tests/Composer/Test/Autoload/Fixtures/platform/typical.php
index 9319e33bd..9a11efd36 100644
--- a/tests/Composer/Test/Autoload/Fixtures/platform/typical.php
+++ b/tests/Composer/Test/Autoload/Fixtures/platform/typical.php
@@ -17,6 +17,9 @@ if ($missingExtensions) {
 }
 
 if ($issues) {
+    if (!headers_sent()) {
+        header('HTTP/1.1 500 Internal Server Error');
+    }
     if (!ini_get('display_errors')) {
         if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
             fwrite(STDERR, 'Composer detected issues in your platform:' . PHP_EOL.PHP_EOL . implode(PHP_EOL, $issues) . PHP_EOL.PHP_EOL);