diff --git a/bin/composer b/bin/composer
index cee476b6d..32c45bcda 100755
--- a/bin/composer
+++ b/bin/composer
@@ -65,6 +65,12 @@ if (function_exists('ini_set')) {
     unset($memoryLimit);
 }
 
+// Workaround PHP bug on Windows where env vars containing Unicode chars are mangled in $_SERVER
+// see https://github.com/php/php-src/issues/7896
+if (Platform::isWindows()) {
+    $_SERVER = array_merge($_SERVER, array_intersect_ukey($_SERVER, getenv(), 'strcasecmp'));
+}
+
 Platform::putEnv('COMPOSER_BINARY', realpath($_SERVER['argv'][0]));
 
 ErrorHandler::register();