diff --git a/dev/tests/static/framework/Magento/Sniffs/NamingConventions/ReservedWordsSniff.php b/dev/tests/static/framework/Magento/Sniffs/NamingConventions/ReservedWordsSniff.php
index f41c235a6c0f8..e3cfdf532438c 100644
--- a/dev/tests/static/framework/Magento/Sniffs/NamingConventions/ReservedWordsSniff.php
+++ b/dev/tests/static/framework/Magento/Sniffs/NamingConventions/ReservedWordsSniff.php
@@ -64,7 +64,7 @@ protected function validateNamespace(File $sourceFile, $stackPtr)
                     'Cannot use "%s" in namespace as it is reserved since PHP %s',
                     $stackPtr,
                     'Namespace',
-                    [$namespacePart, $this->reservedWords[$namespacePart]]
+                    [$namespacePart, $this->reservedWords[strtolower($namespacePart)]]
                 );
             }
             $stackPtr++;