diff --git a/lib/rudder/analytics/client.rb b/lib/rudder/analytics/client.rb
index b1cdf1e..272486e 100644
--- a/lib/rudder/analytics/client.rb
+++ b/lib/rudder/analytics/client.rb
@@ -24,6 +24,7 @@ class Client
       # @option opts [FixNum] :max_queue_size Maximum number of calls to be
       #   remain queued.
       # @option opts [Proc] :on_error Handles error calls from the API.
+      # @option opts [Proc] :on_error_with_messages Handles error calls from the API, with failed messages.
       def initialize(opts = {})
         @config = Configuration.new(opts)
         @queue = Queue.new
diff --git a/lib/rudder/analytics/configuration.rb b/lib/rudder/analytics/configuration.rb
index 8149a1f..0906657 100644
--- a/lib/rudder/analytics/configuration.rb
+++ b/lib/rudder/analytics/configuration.rb
@@ -7,7 +7,7 @@ class Analytics
     class Configuration
       include Rudder::Analytics::Utils
 
-      attr_reader :write_key, :data_plane_url, :on_error, :stub, :gzip, :ssl, :batch_size, :test, :max_queue_size, :backoff_policy, :retries
+      attr_reader :write_key, :data_plane_url, :on_error, :on_error_with_messages, :stub, :gzip, :ssl, :batch_size, :test, :max_queue_size, :backoff_policy, :retries
 
       def initialize(settings = {})
         symbolized_settings = symbolize_keys(settings)
@@ -18,6 +18,7 @@ def initialize(settings = {})
         @max_queue_size = symbolized_settings[:max_queue_size] || Defaults::Queue::MAX_SIZE
         @ssl = symbolized_settings[:ssl]
         @on_error = symbolized_settings[:on_error] || proc { |status, error| }
+        @on_error_with_messages = symbolized_settings[:on_error_with_messages] || proc { |status, error, messages| }
         @stub = symbolized_settings[:stub]
         @batch_size = symbolized_settings[:batch_size] || Defaults::MessageBatch::MAX_SIZE
         @gzip = symbolized_settings[:gzip]
diff --git a/lib/rudder/analytics/message_batch.rb b/lib/rudder/analytics/message_batch.rb
index 60811c5..0d0366e 100644
--- a/lib/rudder/analytics/message_batch.rb
+++ b/lib/rudder/analytics/message_batch.rb
@@ -26,7 +26,7 @@ def <<(message)
           message_json = message.to_json
           # puts message_json
         rescue StandardError => e
-          raise JSONGenerationError, "Serialization error: #{e}"
+          raise JSONGenerationError, "Serialization error: #{e} for message: #{message.inspect}"
         end
 
         message_json_size = message_json.bytesize
diff --git a/lib/rudder/analytics/version.rb b/lib/rudder/analytics/version.rb
index a5e0056..f3f08c4 100644
--- a/lib/rudder/analytics/version.rb
+++ b/lib/rudder/analytics/version.rb
@@ -2,6 +2,6 @@
 
 module Rudder
   class Analytics
-    VERSION = '3.0.1'
+    VERSION = '3.1.0'
   end
 end
diff --git a/lib/rudder/analytics/worker.rb b/lib/rudder/analytics/worker.rb
index ff18190..ae812cf 100644
--- a/lib/rudder/analytics/worker.rb
+++ b/lib/rudder/analytics/worker.rb
@@ -29,6 +29,7 @@ def initialize(queue, config)
         @write_key = config.write_key
         @ssl = config.ssl
         @on_error = config.on_error
+        @on_error_with_messages = config.on_error_with_messages
         @batch = MessageBatch.new(config.batch_size)
         @lock = Mutex.new
         @transport = Transport.new(config)
@@ -46,7 +47,10 @@ def run
 
           # res = Request.new(:data_plane_url => @data_plane_url, :ssl => @ssl).post @write_key, @batch
           res = @transport.send @write_key, @batch
-          @on_error.call(res.status, res.error) unless res.status == 200
+          unless res.status == 200
+            @on_error.call(res.status, res.error) 
+            @on_error_with_messages.call(res.status, res.error, @batch.messages)
+          end
 
           @lock.synchronize { @batch.clear }
         end
@@ -66,6 +70,7 @@ def consume_message_from_queue!
         @batch << @queue.pop
       rescue MessageBatch::JSONGenerationError => e
         @on_error.call(-1, e.to_s)
+        @on_error_with_messages.call(-1, e.to_s, [])
       end
     end
   end
diff --git a/spec/rudder/analytics/worker_spec.rb b/spec/rudder/analytics/worker_spec.rb
index 544f7ee..e752b9a 100644
--- a/spec/rudder/analytics/worker_spec.rb
+++ b/spec/rudder/analytics/worker_spec.rb
@@ -79,6 +79,38 @@ class Analytics
           expect(error).to eq('Some error')
         end
 
+        it 'executes the on_error_with_messages error handler if the request is invalid' do
+          Rudder::Analytics::Transport
+            .any_instance
+            .stub(:send)
+            .and_return(Rudder::Analytics::Response.new(400, 'Some error'))
+
+          status = error = data = nil
+          on_error_with_messages = proc do |yielded_status, yielded_error, yielded_data|
+            sleep 0.2 # Make this take longer than thread spin-up (below)
+            status, error, data = yielded_status, yielded_error, yielded_data.dup
+          end
+
+          message = { context: {:ip=>"127.0.0.1"}, type: "identify", traits: { email: "test@test.com" } }
+          queue = Queue.new
+          queue << message
+          config = Configuration.new({ :on_error_with_messages => on_error_with_messages, :write_key => 'write_key', :data_plane_url => 'data_plane_url' })
+          worker = described_class.new(queue, config)
+
+          # This is to ensure that Client#flush doesn't finish before calling
+          # the error handler.
+          Thread.new { worker.run }
+          sleep 0.1 # First give thread time to spin-up.
+          sleep 0.01 while worker.is_requesting?
+
+          Rudder::Analytics::Transport.any_instance.unstub(:send)
+
+          expect(queue).to be_empty
+          expect(status).to eq(400)
+          expect(error).to eq('Some error')
+          expect(data).to eq([message])
+        end
+
         # it 'does not call on_error if the request is good' do
         #   on_error = proc do |status, error|
         #     puts "#{status}, #{error}"