diff --git a/.ci/docker-setup.sh b/.ci/docker-setup.sh
index 08bd3585..8e03b1c9 100755
--- a/.ci/docker-setup.sh
+++ b/.ci/docker-setup.sh
@@ -48,10 +48,10 @@ if [ "$ELASTIC_STACK_VERSION" ]; then
 
     if [ "$INTEGRATION" == "true" ]; then
         docker-compose down
-        docker-compose build
+        docker-compose build --quiet
     else
         docker-compose down
-        docker-compose build logstash
+        docker-compose build logstash --quiet
     fi
 else
     echo "Please set the ELASTIC_STACK_VERSION environment variable"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1071291d..c193b44c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 11.4.2
+ - Fixes an issue where events containing non-unicode strings could fail to serialize correctly when compression is enabled [#1169](https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/1169)
+
 ## 11.4.1
  - Feat: upgrade manticore (http-client) library [#1063](https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/1063)
    - the underlying changes include latest HttpClient (4.5.13)
diff --git a/docs/index.asciidoc b/docs/index.asciidoc
index 85be8c8f..306aa6d3 100644
--- a/docs/index.asciidoc
+++ b/docs/index.asciidoc
@@ -293,6 +293,11 @@ index level and `monitoring` permissions at cluster level. The `monitoring`
 permission at cluster level is necessary to perform periodic connectivity
 checks.
 
+[id="plugins-{type}s-{plugin}-handling-non-utf-8"]
+==== Handling non UTF-8 data
+
+This plugin transmits events to Elasticsearch using a JSON API, and therefore requires that all string values in events to be valid UTF-8.
+When a string value on an event contains one or more byte sequences that are not valid in UTF-8, each offending byte sequence is replaced with the UTF-8 replacement character (`\uFFFD`).
 
 [id="plugins-{type}s-{plugin}-options"]
 ==== Elasticsearch Output Configuration Options
diff --git a/lib/logstash/outputs/elasticsearch/http_client.rb b/lib/logstash/outputs/elasticsearch/http_client.rb
index 9efaeaf1..ee2c9477 100644
--- a/lib/logstash/outputs/elasticsearch/http_client.rb
+++ b/lib/logstash/outputs/elasticsearch/http_client.rb
@@ -127,6 +127,9 @@ def bulk(actions)
                     action.map {|line| LogStash::Json.dump(line)}.join("\n") :
                     LogStash::Json.dump(action)
         as_json << "\n"
+
+        as_json.scrub! # ensure generated JSON is valid UTF-8
+
         if (stream_writer.pos + as_json.bytesize) > TARGET_BULK_BYTES && stream_writer.pos > 0
           stream_writer.flush # ensure writer has sync'd buffers before reporting sizes
           logger.debug("Sending partial bulk request for batch with one or more actions remaining.",
diff --git a/logstash-output-elasticsearch.gemspec b/logstash-output-elasticsearch.gemspec
index eb33f432..2be78537 100644
--- a/logstash-output-elasticsearch.gemspec
+++ b/logstash-output-elasticsearch.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name            = 'logstash-output-elasticsearch'
-  s.version         = '11.4.1'
+  s.version         = '11.4.2'
 
   s.licenses        = ['apache-2.0']
   s.summary         = "Stores logs in Elasticsearch"
diff --git a/spec/integration/outputs/compressed_indexing_spec.rb b/spec/integration/outputs/compressed_indexing_spec.rb
index 4a57f323..37475031 100644
--- a/spec/integration/outputs/compressed_indexing_spec.rb
+++ b/spec/integration/outputs/compressed_indexing_spec.rb
@@ -10,10 +10,12 @@
 
 describe "indexing with http_compression turned on", :integration => true do
   let(:event) { LogStash::Event.new("message" => "Hello World!", "type" => type) }
+  let(:event_with_invalid_utf_8_bytes) { LogStash::Event.new("message" => "Message from spacecraft which contains \xAC invalid \xD7 byte sequences.", "type" => type) }
   let(:index) { 10.times.collect { rand(10).to_s }.join("") }
   let(:type) { ESHelper.es_version_satisfies?("< 7") ? "doc" : "_doc" }
   let(:event_count) { 10000 + rand(500) }
-  let(:events) { event_count.times.map { event }.to_a }
+  # mix the events with valid and invalid UTF-8 payloads
+  let(:events) { event_count.times.map { |i| i%3 == 0 ? event : event_with_invalid_utf_8_bytes }.to_a }
   let(:config) {
     {
       "hosts" => get_host_port,
diff --git a/spec/unit/outputs/elasticsearch/http_client_spec.rb b/spec/unit/outputs/elasticsearch/http_client_spec.rb
index 16b84424..15774d8e 100644
--- a/spec/unit/outputs/elasticsearch/http_client_spec.rb
+++ b/spec/unit/outputs/elasticsearch/http_client_spec.rb
@@ -243,12 +243,14 @@
           end
         end
 
-        context "with two messages" do
-          let(:message1) { "hey" }
-          let(:message2) { "you" }
+        context "with multiple messages" do
+          let(:message_head) { "Spacecraft message" }
+          let(:message_tail) { "byte sequence" }
+          let(:invalid_utf_8_message) { "contains invalid \xAC" }
           let(:actions) { [
-            ["index", {:_id=>nil, :_index=>"logstash"}, {"message"=> message1}],
-            ["index", {:_id=>nil, :_index=>"logstash"}, {"message"=> message2}],
+            ["index", {:_id=>nil, :_index=>"logstash"}, {"message"=> message_head}],
+            ["index", {:_id=>nil, :_index=>"logstash"}, {"message"=> invalid_utf_8_message}],
+            ["index", {:_id=>nil, :_index=>"logstash"}, {"message"=> message_tail}],
           ]}
           it "executes one bulk_send operation" do
             allow(subject).to receive(:join_bulk_responses)
@@ -258,7 +260,7 @@
 
           context "if one exceeds TARGET_BULK_BYTES" do
             let(:target_bulk_bytes) { LogStash::Outputs::ElasticSearch::TARGET_BULK_BYTES }
-            let(:message1) { "a" * (target_bulk_bytes + 1) }
+            let(:message_head) { "a" * (target_bulk_bytes + 1) }
             it "executes two bulk_send operations" do
               allow(subject).to receive(:join_bulk_responses)
               expect(subject).to receive(:bulk_send).twice