diff --git a/src/Request/Parser.php b/src/Request/Parser.php
index 7ff1200a1..8f3ebca0e 100644
--- a/src/Request/Parser.php
+++ b/src/Request/Parser.php
@@ -54,7 +54,7 @@ private function getParsedBody(Request $request): array
 
                 $parsedBody = json_decode($body, true);
 
-                if (JSON_ERROR_NONE !== json_last_error()) {
+                if (JSON_ERROR_NONE !== json_last_error() || is_string($parsedBody)) {
                     throw new BadRequestHttpException('POST body sent invalid JSON');
                 }
                 break;