1 files changed, 5 insertions, 2 deletions
diff --git a/aws/aws-sdk-php/src/Api/Serializer/RestJsonSerializer.php b/aws/aws-sdk-php/src/Api/Serializer/RestJsonSerializer.php
index acc59638..8a2aa993 100644
--- a/aws/aws-sdk-php/src/Api/Serializer/RestJsonSerializer.php
+++ b/aws/aws-sdk-php/src/Api/Serializer/RestJsonSerializer.php
@@ -27,13 +27,16 @@ class RestJsonSerializer extends RestSerializer
         JsonBody $jsonFormatter = null
     ) {
         parent::__construct($api, $endpoint);
-        $this->contentType = 'application/json';
+        $this->contentType = JsonBody::getContentType($api);
         $this->jsonFormatter = $jsonFormatter ?: new JsonBody($api);
     }
 
     protected function payload(StructureShape $member, array $value, array &$opts)
     {
+        $body = isset($value) ?
+            ((string) $this->jsonFormatter->build($member, $value))
+            : "{}";
         $opts['headers']['Content-Type'] = $this->contentType;
-        $opts['body'] = (string) $this->jsonFormatter->build($member, $value);
+        $opts['body'] = $body;
     }
 }