diff --git a/elasticsearch/lib/elasticsearch.rb b/elasticsearch/lib/elasticsearch.rb
index 3e55285ad9..fc54bae1c8 100644
--- a/elasticsearch/lib/elasticsearch.rb
+++ b/elasticsearch/lib/elasticsearch.rb
@@ -180,11 +180,15 @@ def set_user_agent!(arguments)
     end
 
     def set_content_type!(arguments)
-      headers = {
-        'content-type' => 'application/vnd.elasticsearch+json; compatible-with=9',
-        'accept' => 'application/vnd.elasticsearch+json; compatible-with=9'
-      }
-      set_header(headers, arguments)
+      headers = {}
+      user_headers = arguments&.[](:transport_options)&.[](:headers)
+      unless user_headers&.keys&.detect { |h| h =~ /content-?_?type/ }
+        headers['content-type'] = 'application/vnd.elasticsearch+json; compatible-with=9'
+      end
+      unless user_headers&.keys&.detect { |h| h =~ /accept/ }
+        headers['accept'] = 'application/vnd.elasticsearch+json; compatible-with=9'
+      end
+      set_header(headers, arguments) unless headers.empty?
     end
 
     def set_header(header, arguments)
diff --git a/elasticsearch/spec/unit/headers_spec.rb b/elasticsearch/spec/unit/headers_spec.rb
index 48a072b2fc..3751c74488 100644
--- a/elasticsearch/spec/unit/headers_spec.rb
+++ b/elasticsearch/spec/unit/headers_spec.rb
@@ -52,4 +52,73 @@
       client.search(headers: param_headers)
     end
   end
+
+  context 'when accept header is changed' do
+    let!(:client) do
+      described_class.new(
+        host: 'http://localhost:9200',
+        transport_options: { headers: instance_headers }
+      ).tap do |client|
+        client.instance_variable_set('@verified', true)
+      end
+    end
+    let(:instance_headers) do
+      { accept: 'application/json' }
+    end
+
+    it 'performs the request with the header' do
+      connection_headers = client.transport.connections.connections.first.connection.headers
+      expect(connection_headers['Accept']).to eq 'application/json'
+      expect(connection_headers['Content-Type']).to eq 'application/vnd.elasticsearch+json; compatible-with=9'
+
+      expect_any_instance_of(Faraday::Connection)
+        .to receive(:run_request)
+              .with(:get, 'http://localhost:9200/_search', nil, connection_headers) { OpenStruct.new(body: '') }
+      client.search
+    end
+  end
+
+  context 'when content-type header is changed' do
+    let!(:client) do
+      described_class.new(
+        host: 'http://localhost:9200',
+        transport_options: { headers: instance_headers }
+      ).tap do |client|
+        client.instance_variable_set('@verified', true)
+      end
+    end
+    let(:instance_headers) do
+      { content_type: 'application/json' }
+    end
+
+    it 'performs the request with the header' do
+      connection_headers = client.transport.connections.connections.first.connection.headers
+      expect(connection_headers['Accept']).to eq 'application/vnd.elasticsearch+json; compatible-with=9'
+      expect(connection_headers['Content-Type']).to eq 'application/json'
+
+      expect_any_instance_of(Faraday::Connection)
+        .to receive(:run_request)
+              .with(:get, 'http://localhost:9200/_search', nil, connection_headers) { OpenStruct.new(body: '') }
+      client.search
+    end
+  end
+
+  context 'when no header is set, uses v9 content-type and accept' do
+    let!(:client) do
+      described_class.new(host: 'http://localhost:9200').tap do |client|
+        client.instance_variable_set('@verified', true)
+      end
+    end
+
+    it 'performs the request with the header' do
+      expected_headers = client.transport.connections.connections.first.connection.headers
+      expect(expected_headers['Accept']).to eq 'application/vnd.elasticsearch+json; compatible-with=9'
+      expect(expected_headers['Content-Type']).to eq 'application/vnd.elasticsearch+json; compatible-with=9'
+
+      expect_any_instance_of(Faraday::Connection)
+        .to receive(:run_request)
+              .with(:get, 'http://localhost:9200/_search', nil, expected_headers) { OpenStruct.new(body: '') }
+      client.search
+    end
+  end
 end