diff --git a/elasticsearch-api/lib/elasticsearch/api.rb b/elasticsearch-api/lib/elasticsearch/api.rb
index 7504667e3..7d5913da7 100644
--- a/elasticsearch-api/lib/elasticsearch/api.rb
+++ b/elasticsearch-api/lib/elasticsearch/api.rb
@@ -29,7 +29,19 @@ module Elasticsearch
   module API
     include Elasticsearch::API::Actions
 
-    DEFAULT_SERIALIZER = MultiJson
+    # Default JSON serializer. multi_json >= 1.21 deprecates the MultiJson constant and
+    # dump/load in favor of MultiJSON, generate/parse; use the new API when available.
+    module DefaultSerializer
+      def self.dump(object, options = {})
+        defined?(::MultiJSON) ? ::MultiJSON.generate(object, options) : ::MultiJson.dump(object, options)
+      end
+
+      def self.load(string, options = {})
+        defined?(::MultiJSON) ? ::MultiJSON.parse(string, options) : ::MultiJson.load(string, options)
+      end
+    end
+
+    DEFAULT_SERIALIZER = DefaultSerializer
 
     HTTP_GET          = 'GET'.freeze
     HTTP_HEAD         = 'HEAD'.freeze
diff --git a/elasticsearch-api/spec/unit/api_spec.rb b/elasticsearch-api/spec/unit/api_spec.rb
index 06aebc88c..a61f62ac6 100644
--- a/elasticsearch-api/spec/unit/api_spec.rb
+++ b/elasticsearch-api/spec/unit/api_spec.rb
@@ -24,7 +24,16 @@
     end
 
     it 'has a default serializer' do
-      expect(Elasticsearch::API.serializer).to eq(MultiJson)
+      expect(Elasticsearch::API.serializer).to respond_to(:dump, :load)
+    end
+
+    it 'serializes and deserializes with the default serializer' do
+      serializer = Elasticsearch::API::DEFAULT_SERIALIZER
+      expect(serializer.load(serializer.dump({ 'a' => 1 }))).to eq({ 'a' => 1 })
+    end
+
+    it 'does not emit deprecation warnings' do
+      expect { Elasticsearch::API::DEFAULT_SERIALIZER.dump({ a: 1 }) }.not_to output.to_stderr
     end
 
     context 'when settings are changed' do