diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index 7c989098f..7919c29d9 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -12,6 +12,7 @@
 
 namespace Composer\Console;
 
+use Composer\Installer;
 use Composer\IO\NullIO;
 use Composer\Util\Filesystem;
 use Composer\Util\Platform;
@@ -441,6 +442,13 @@ class Application extends BaseApplication
                 return max(1, $e->getCode());
             }
 
+            // override TransportException's code for the purpose of parent::run() using it as process exit code
+            // as http error codes are all beyond the 255 range of permitted exit codes
+            if ($e instanceof TransportException) {
+                $reflProp = new \ReflectionProperty($e, 'code');
+                $reflProp->setValue($e, Installer::ERROR_TRANSPORT_EXCEPTION);
+            }
+
             throw $e;
         } finally {
             restore_error_handler();
diff --git a/src/Composer/Installer.php b/src/Composer/Installer.php
index 32a149856..5f07b0e17 100644
--- a/src/Composer/Installer.php
+++ b/src/Composer/Installer.php
@@ -80,8 +80,8 @@ class Installer
     // used/declared in SolverProblemsException, carried over here for completeness
     public const ERROR_DEPENDENCY_RESOLUTION_FAILED = 2;
     public const ERROR_AUDIT_FAILED = 5;
-    // technically exceptions are thrown with various status codes >400, but the process exit code is normalized to 255
-    public const ERROR_TRANSPORT_EXCEPTION = 255;
+    // technically exceptions are thrown with various status codes >400, but the process exit code is normalized to 100
+    public const ERROR_TRANSPORT_EXCEPTION = 100;
 
     /**
      * @var IOInterface