diff --git a/lib/active_model/array_serializer.rb b/lib/active_model/array_serializer.rb
index 8a42e18a1..b314dbfcd 100644
--- a/lib/active_model/array_serializer.rb
+++ b/lib/active_model/array_serializer.rb
@@ -25,7 +25,8 @@ def initialize(object, options={})
 
     def json_key
       key = root.nil? ? @resource_name : root
-      key_format == :lower_camel ? key.camelize(:lower) : key
+
+      key_format == :lower_camel && key.present? ? key.camelize(:lower) : key
     end
 
     def serializer_for(item)
diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index bd1a3ac55..8a0e856ed 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -126,7 +126,7 @@ def json_key
         root
       end
 
-      key_format == :lower_camel ? key.camelize(:lower) : key
+      key_format == :lower_camel && key.present? ? key.camelize(:lower) : key
     end
 
     def attributes
diff --git a/test/integration/action_controller/serialization_test.rb b/test/integration/action_controller/serialization_test.rb
index 9065e211f..5d1736063 100644
--- a/test/integration/action_controller/serialization_test.rb
+++ b/test/integration/action_controller/serialization_test.rb
@@ -210,6 +210,43 @@ def test_render_array
       end
     end
 
+    class LowerCamelWoRootSerializerTest < ActionController::TestCase
+      class WebLogController < ActionController::Base
+        def render_without_root
+          render json: WebLog.new({name: 'Name 1', display_name: 'Display Name 1'}), 
+                 root: false, 
+                 serializer: WebLogLowerCamelSerializer
+        end
+      end
+
+      tests WebLogController
+
+      def test_render_without_root
+        get :render_without_root
+        assert_equal 'application/json', @response.content_type
+        assert_equal '{"name":"Name 1","displayName":"Display Name 1"}', @response.body
+      end
+    end
+
+    class LowerCamelArrayWoRootSerializerTest < ActionController::TestCase
+      class WebLogController < ActionController::Base
+        def render_array_without_root
+          render json: [WebLog.new({name: 'Name 1', display_name: 'Display Name 1'}), 
+                        WebLog.new({name: 'Name 2', display_name: 'Display Name 2'})], 
+                 root: false, 
+                 each_serializer: WebLogLowerCamelSerializer
+        end
+      end
+
+      tests WebLogController
+
+      def test_render_array_without_root
+        get :render_array_without_root
+        assert_equal 'application/json', @response.content_type
+        assert_equal '[{"name":"Name 1","displayName":"Display Name 1"},{"name":"Name 2","displayName":"Display Name 2"}]', @response.body
+      end
+    end
+
     class ArrayEmbedingSerializerTest < ActionController::TestCase
       def setup
         super