diff --git a/src/JsonApi/Request/JsonApiRequest.php b/src/JsonApi/Request/JsonApiRequest.php
index 6ba98c1..91975e9 100644
--- a/src/JsonApi/Request/JsonApiRequest.php
+++ b/src/JsonApi/Request/JsonApiRequest.php
@@ -31,7 +31,6 @@
 use function strlen;
 use function strpos;
 use function strtolower;
-use function strtoupper;
 use function substr;
 use function trim;