diff --git a/.travis.yml b/.travis.yml
index 6b91070e..6a014fae 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,6 @@ cache:
 rvm:
   - 1.9.3
   - 2.0.0
-  - 2.1
   - 2.2
   - ruby-head
   - rbx-2
@@ -17,7 +16,7 @@ install:
   - bundle install --retry=3
 
 script:
-  - env CAPTURE_STDERR=false bundle exec rake ci
+  - env CAPTURE_STDERR=${CAPTURE_STDERR:-false} bundle exec rake ci
 
 env:
   - "RAILS_VERSION=4.0"
@@ -27,6 +26,8 @@ env:
 
 matrix:
   include:
+  - rvm: 2.1
+    env: CAPTURE_STDERR=true
   - rvm: jruby-19mode
     env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false -Xcli.debug=true --debug'
   allow_failures:
diff --git a/lib/active_model/serializer/array_serializer.rb b/lib/active_model/serializer/array_serializer.rb
index dc95d941..97efa864 100644
--- a/lib/active_model/serializer/array_serializer.rb
+++ b/lib/active_model/serializer/array_serializer.rb
@@ -2,7 +2,7 @@ require 'active_model/serializer/collection_serializer'
 class ActiveModel::Serializer
   class ArraySerializer < CollectionSerializer
     def initialize(*)
-      warn "Calling deprecated ArraySerializer in #{caller[0]}. Please use CollectionSerializer"
+      warn "Calling deprecated ArraySerializer in #{caller[0..2].join(', ')}. Please use CollectionSerializer"
       super
     end
   end
diff --git a/test/array_serializer_test.rb b/test/array_serializer_test.rb
index 233756c4..1ffde04b 100644
--- a/test/array_serializer_test.rb
+++ b/test/array_serializer_test.rb
@@ -3,19 +3,35 @@ require_relative 'collection_serializer_test'
 
 module ActiveModel
   class Serializer
-    class ArraySerializerTest < CollectionSerializerTest
-      extend ActiveSupport::Testing::Stream
-      def self.run_one_method(*)
-        stderr = (capture(:stderr) do
-          super
-        end)
-        if stderr !~ /Calling deprecated ArraySerializer/
-          fail Minitest::Assertion, stderr
+    # Minitest.run_one_method isn't present in minitest 4
+    if $minitest_version > 4 # rubocop:disable Style/GlobalVars
+      class ArraySerializerTest < CollectionSerializerTest
+        extend ActiveSupport::Testing::Stream
+        def self.run_one_method(*)
+          stderr = (capture(:stderr) do
+            super
+          end)
+          if stderr !~ /Calling deprecated ArraySerializer/
+            fail Minitest::Assertion, stderr
+          end
+        end
+
+        def collection_serializer
+          ArraySerializer
         end
       end
-
-      def collection_serializer
-        ArraySerializer
+    else
+      class ArraySerializerTest < Minitest::Test
+        extend ActiveSupport::Testing::Stream
+        def test_json_key_with_root_warns_when_using_array_serializer
+          stderr = (capture(:stderr) do
+            comment = Comment.new
+            post = Post.new
+            serializer = ArraySerializer.new([comment, post])
+            assert_equal serializer.json_key, 'comments'
+          end)
+          assert_match(/Calling deprecated ArraySerializer/, stderr)
+        end
       end
     end
   end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 6495d251..9257c24a 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -25,10 +25,12 @@ require 'minitest/autorun'
 require 'minitest/reporters'
 Minitest::Reporters.use!
 if defined?(Minitest::Test)
+  $minitest_version = 5 # rubocop:disable Style/GlobalVars
   # Minitest 5
   # https://github.com/seattlerb/minitest/blob/e21fdda9d/lib/minitest/autorun.rb
   # https://github.com/seattlerb/minitest/blob/e21fdda9d/lib/minitest.rb#L45-L59
 else
+  $minitest_version = 4 # rubocop:disable Style/GlobalVars
   # Minitest 4
   # https://github.com/seattlerb/minitest/blob/644a52fd0/lib/minitest/autorun.rb
   # https://github.com/seattlerb/minitest/blob/644a52fd0/lib/minitest/unit.rb#L768-L787
@@ -47,6 +49,8 @@ end
 if ENV['CAPTURE_STDERR'] !~ /false|1/i
   require 'capture_warnings'
   CaptureWarnings.new(_fail_build = true).execute!
+else
+  $VERBOSE = true
 end
 
 require 'active_model_serializers'