diff --git a/test/ServerRequestFactoryTest.php b/test/ServerRequestFactoryTest.php
index 003b8aec..fded011d 100644
--- a/test/ServerRequestFactoryTest.php
+++ b/test/ServerRequestFactoryTest.php
@@ -295,7 +295,7 @@ public function testMarshalUriDetectsHttpsSchemeFromServerValue($param)
         $request = $request->withHeader('Host', 'example.com');
 
         $server  = [
-            $param => true,
+            $param => 'on',
         ];
 
         $uri = marshalUriFromSapi($server, $request->getHeaders());