diff --git a/.ruby-version b/.ruby-version
index e261122..fd2a018 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.6.7
+3.1.0
diff --git a/Gemfile b/Gemfile
index a662dfc..ff2deec 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,3 +6,5 @@ gemspec
 rails_version = ENV['RAILS_VERSION'] || '6.0.2'
 
 gem 'activesupport', "~> #{rails_version}"
+gem 'rack'
+gem 'rexml'
diff --git a/lib/dox/printers/example_request_printer.rb b/lib/dox/printers/example_request_printer.rb
index 9f63440..71bfaa0 100644
--- a/lib/dox/printers/example_request_printer.rb
+++ b/lib/dox/printers/example_request_printer.rb
@@ -47,7 +47,7 @@ def add_schema(body, path)
       end
 
       def find_headers(headers)
-        headers.find { |key, _| key == 'Accept' }&.last || 'any'
+        headers.find { |key, _| key == 'Content-Type' }&.last || 'any'
       end
 
       def acquire_header_params
diff --git a/spec/fixtures/example.json b/spec/fixtures/example.json
index e715f27..0e50941 100644
--- a/spec/fixtures/example.json
+++ b/spec/fixtures/example.json
@@ -18,6 +18,11 @@
             "name": "Accept",
             "in": "header",
             "example": "application/json"
+          },
+          {
+            "name": "Content-Type",
+            "in": "header",
+            "example": "application/json"
           }
         ],
         "responses": {
@@ -61,6 +66,11 @@
             "name": "Accept",
             "in": "header",
             "example": "application/json"
+          },
+          {
+            "name": "Content-Type",
+            "in": "header",
+            "example": "application/json"
           }
         ],
         "requestBody": {
@@ -132,6 +142,11 @@
             "name": "Accept",
             "in": "header",
             "example": "application/json"
+          },
+          {
+            "name": "Content-Type",
+            "in": "header",
+            "example": "application/json"
           }
         ],
         "responses": {
@@ -176,6 +191,11 @@
             "name": "Accept",
             "in": "header",
             "example": "application/json"
+          },
+          {
+            "name": "Content-Type",
+            "in": "header",
+            "example": "application/json"
           }
         ],
         "responses": {
diff --git a/spec/formatter_spec.rb b/spec/formatter_spec.rb
index 3f895ed..12bce96 100644
--- a/spec/formatter_spec.rb
+++ b/spec/formatter_spec.rb
@@ -24,7 +24,7 @@
         path: '/pokemons/14',
         fullpath: '/pokemons/14',
         path_parameters: { id: 14 },
-        headers: { 'Accept' => 'application/json' }
+        headers: { 'Accept' => 'application/json', 'Content-Type' => 'application/json' }
       },
       response: {
         status: 200,
@@ -64,7 +64,7 @@
             }
           }
         },
-        headers: { 'Accept' => 'application/json' }
+        headers: { 'Accept' => 'application/json', 'Content-Type' => 'application/json' }
       },
       response: {
         status: 201,
@@ -97,7 +97,7 @@
         method: 'get',
         path: '/digimons',
         fullpath: '/digimons',
-        headers: { 'Accept' => 'application/json' }
+        headers: { 'Accept' => 'application/json', 'Content-Type' => 'application/json' }
       },
       response: {
         status: 200,
@@ -139,7 +139,7 @@
         method: 'get',
         path: '/auth',
         fullpath: '/auth',
-        headers: { 'Accept' => 'application/json' }
+        headers: { 'Accept' => 'application/json', 'Content-Type' => 'application/json' }
       },
       response: {
         status: 200,
diff --git a/spec/printers/example_request_printer_spec.rb b/spec/printers/example_request_printer_spec.rb
index 94b26cc..d038433 100644
--- a/spec/printers/example_request_printer_spec.rb
+++ b/spec/printers/example_request_printer_spec.rb
@@ -56,7 +56,7 @@
         )
       end
 
-      let(:req_headers) { { 'Accept' => content_type } }
+      let(:req_headers) { { 'Content-Type' => content_type, 'Accept' => content_type } }
 
       before do
         Dox.config.headers_whitelist = nil