diff --git a/lib/microsoft/graph.rb b/lib/microsoft/graph.rb
index 0686aaf..dd2d484 100644
--- a/lib/microsoft/graph.rb
+++ b/lib/microsoft/graph.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "httparty"
+require "ostruct"
 require "securerandom"
 require_relative "graph/version"
 require_relative "graph/batch"
@@ -51,7 +52,7 @@ def call(endpoint, token: @token, method: "GET", headers: {}, params: nil, body:
         url,
         headers: headers,
         query: params,
-        body: @body_formatter.call(body, method: method).to_json,
+        body: @body_formatter.call(body, method: method),
         parser: InstanceParser
       )
 
diff --git a/lib/microsoft/graph/body_formatter.rb b/lib/microsoft/graph/body_formatter.rb
index 9b8f59d..b6668a3 100644
--- a/lib/microsoft/graph/body_formatter.rb
+++ b/lib/microsoft/graph/body_formatter.rb
@@ -6,8 +6,9 @@ class BodyFormatter
       def call(body, method:)
         return nil unless Microsoft::Graph::BODY_METHODS.include?(method)
         return nil unless body
+        return body unless body.is_a?(Hash)
 
-        body.transform_keys(&method(:camelize))
+        body.transform_keys(&method(:camelize)).to_json
       end
 
       private