diff --git a/.ci/docker-run.sh b/.ci/docker-run.sh
index 02f0c42c..72baaba9 100755
--- a/.ci/docker-run.sh
+++ b/.ci/docker-run.sh
@@ -6,7 +6,8 @@ set -ex
 cd .ci
 
 if [ "$INTEGRATION" == "true" ]; then
-    docker-compose up --exit-code-from logstash
+    # remove the `--attach logstash` if you want to see all logs including elasticsearch container logs
+    docker-compose up --exit-code-from logstash --attach logstash
 else
     docker-compose up --exit-code-from logstash logstash
 fi
diff --git a/.ci/docker-setup.sh b/.ci/docker-setup.sh
index 08bd3585..8e03b1c9 100755
--- a/.ci/docker-setup.sh
+++ b/.ci/docker-setup.sh
@@ -48,10 +48,10 @@ if [ "$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/fixtures/test_certs/ca.crt b/spec/fixtures/test_certs/ca.crt
index d3a1abb6..6626206b 100644
--- a/spec/fixtures/test_certs/ca.crt
+++ b/spec/fixtures/test_certs/ca.crt
@@ -1,32 +1,31 @@
 -----BEGIN CERTIFICATE-----
-MIIFeTCCA2GgAwIBAgIUU+VHJ91JsLLA1GJYC+UchNfw3hEwDQYJKoZIhvcNAQEL
-BQAwTDELMAkGA1UEBhMCUFQxCzAJBgNVBAgMAk5BMQ8wDQYDVQQHDAZMaXNib24x
-DjAMBgNVBAoMBU15TGFiMQ8wDQYDVQQDDAZSb290Q0EwHhcNMTkwNzE1MTMxMTI5
-WhcNMjQwNzE0MTMxMTI5WjBMMQswCQYDVQQGEwJQVDELMAkGA1UECAwCTkExDzAN
-BgNVBAcMBkxpc2JvbjEOMAwGA1UECgwFTXlMYWIxDzANBgNVBAMMBlJvb3RDQTCC
-AiIwDQYJKoZIhvcNAQEBBQADggIPADCCAgoCggIBAMtTMqAWuH17b9XqPa5L3HNq
-gnZ958+gvcOt7Q/sOEvcDQJgkzZ+Gywh5er5JF2iomYOHiD5JncYr4YmRQKuYfD6
-B1WI5FuQthD/OlA1/RHqtbY27J33SaO66ro8gal7vjHrXKQkefVYRwdfO6DqqbhV
-6L4sMiy8FzQ55TMpoM35cWuvoAMxvSQqGZ4pYYKnfNSGhzHvssfNS1xu/Lwb7Vju
-4jPhp+43BkGwEimI5km7jNC1nwjiHtxDsY/s93AKa/vLktXKUK5nA3jjJOhAbRTV
-nbOAgxFt0YbX98xW/aUqscgBUVs9J/MyTRMwVKJ7Vsmth1PdJQksUASuzESlSPl0
-9dMjTQ+MXzJDt0JvX8SIJPmbBng78MSaCUhpOZiii1l2mBfPWejx20I/SMCUNmzb
-wm2w9JD50Jv2iX4l4ge4H1CIK1/orW1pdY9xPL0uKYm6ADsDC0B8sGgNMBXeB6aL
-ojY1/ITwmmfpfk9c/yWPfC7stHgCYRAv5MfGAsmv0/ya5VrWQGBJkFiYy1pon6nx
-UjCbgn0RABojRoGdhhY3QDipgwmSgFZxr064RFr1bt/Ml3MJmPf535mSwPdk/j/z
-w4IZTvlmwKW3FyMDhwYL/zX7J0c6MzMPLEdi73Qjzmr3ENIrir4O86wNz81YRfYk
-g9ZX8yKJK9LBAUrYCjJ3AgMBAAGjUzBRMB0GA1UdDgQWBBShWnSceOrqYn9Qa4WG
-dIrvKNs/KzAfBgNVHSMEGDAWgBShWnSceOrqYn9Qa4WGdIrvKNs/KzAPBgNVHRMB
-Af8EBTADAQH/MA0GCSqGSIb3DQEBCwUAA4ICAQBRQK0m3t5h2Y3CUCJYLMiCUge4
-UOzvpCoawSXH1FP2ycA+P1bP8H8htjwvV334ZADlQrDQRu0hqa1T+DxwhLxNOxgE
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-jjTOV2S71edVlKTxRLZpHgoTZpBL/phwRQ63vdef4ftNGs0glGDc0yqXGMxMALOl
-Up7+H4HI99rldZcul6oZ+ORltt047Hk7ctWb20SqxEH9tGLXKm6hDEL9HzyFXeyJ
-DAue1GF+3H0KvsjSs5XH7LHMuJDCuSP64+h9gzkI+q06oBNX/9pQyQaHj0K4don8
-lWOMLI4gQibV7R1Opt2feA8MwWxouP/yni8IX6sPePVQ+fLEk1C+Kg+x6k1yQHEM
-36BEP6iYOYvqG0OIjMas2U7Yhn2wWlVm9It3WMyaW8ZPI8kwc3dx715dZuNg/zjd
-rJS678BNBVxInc7dzpY6el0Lr70CGwiJpX/N9P1yiTFZ7GZm3Kax8QnTtvqXzRIy
-sBgt8BVZHUe1lWFYlG+jlakiXqz752nmHuwif7iBI4iWzRmW2vYPfTEmYPRLZES2
-nIg9fQPvVw+fIHACZQ==
+MIIFRTCCAy2gAwIBAgIBATANBgkqhkiG9w0BAQsFADBMMQswCQYDVQQGEwJQVDEL
+MAkGA1UECAwCTkExDzANBgNVBAcMBkxpc2JvbjEOMAwGA1UECgwFTXlMYWIxDzAN
+BgNVBAMMBlJvb3RDQTAeFw0yNDAzMTkyMjM3MTdaFw0yNTAzMTkyMjM3MTdaMEwx
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+Nn4bLCHl6vkkXaKiZg4eIPkmdxivhiZFAq5h8PoHVYjkW5C2EP86UDX9Eeq1tjbs
+nfdJo7rqujyBqXu+MetcpCR59VhHB187oOqpuFXoviwyLLwXNDnlMymgzflxa6+g
+AzG9JCoZnilhgqd81IaHMe+yx81LXG78vBvtWO7iM+Gn7jcGQbASKYjmSbuM0LWf
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+eDvwxJoJSGk5mKKLWXaYF89Z6PHbQj9IwJQ2bNvCbbD0kPnQm/aJfiXiB7gfUIgr
+X+itbWl1j3E8vS4piboAOwMLQHywaA0wFd4HpouiNjX8hPCaZ+l+T1z/JY98Luy0
+eAJhEC/kx8YCya/T/JrlWtZAYEmQWJjLWmifqfFSMJuCfREAGiNGgZ2GFjdAOKmD
+CZKAVnGvTrhEWvVu38yXcwmY9/nfmZLA92T+P/PDghlO+WbApbcXIwOHBgv/Nfsn
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+7yjbPyswDQYJKoZIhvcNAQELBQADggIBADeI0gRfzF5zyhCCmtlA44L1fo3BEYtm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 -----END CERTIFICATE-----
diff --git a/spec/fixtures/test_certs/renew.sh b/spec/fixtures/test_certs/renew.sh
new file mode 100755
index 00000000..57783263
--- /dev/null
+++ b/spec/fixtures/test_certs/renew.sh
@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -e
+cd "$(dirname "$0")"
+
+openssl x509 -x509toreq -copy_extensions copyall -in ca.crt -signkey ca.key -out ca.csr
+openssl x509 -req -copy_extensions copyall -days 365 -in ca.csr -set_serial 0x01 -signkey ca.key -out ca.crt && rm ca.csr
+
+openssl x509 -x509toreq -copy_extensions copyall -in test.crt -signkey test.key -out test.csr
+openssl x509 -req -copy_extensions copyall -days 365 -in test.csr -set_serial 0x01 -CA ca.crt -CAkey ca.key -out test.crt && rm test.csr
+openssl pkcs12 -export -inkey test.key -in test.crt -passout "pass:1234567890" -out test.p12
diff --git a/spec/fixtures/test_certs/test.crt b/spec/fixtures/test_certs/test.crt
index 11d4a238..6aa035aa 100644
--- a/spec/fixtures/test_certs/test.crt
+++ b/spec/fixtures/test_certs/test.crt
@@ -1,7 +1,7 @@
 -----BEGIN CERTIFICATE-----
-MIIGQjCCBCqgAwIBAgIBAzANBgkqhkiG9w0BAQsFADBMMQswCQYDVQQGEwJQVDEL
+MIIF1jCCA76gAwIBAgIBATANBgkqhkiG9w0BAQsFADBMMQswCQYDVQQGEwJQVDEL
 MAkGA1UECAwCTkExDzANBgNVBAcMBkxpc2JvbjEOMAwGA1UECgwFTXlMYWIxDzAN
-BgNVBAMMBlJvb3RDQTAeFw0xOTA3MTUxMzEzMDVaFw0yMjA0MTAxMzEzMDVaMFMx
+BgNVBAMMBlJvb3RDQTAeFw0yNDAzMTkyMjM3MTdaFw0yNTAzMTkyMjM3MTdaMFMx
 CzAJBgNVBAYTAlBUMQswCQYDVQQIDAJOQTEPMA0GA1UEBwwGTGlzYm9uMQ4wDAYD
 VQQKDAVNeUxhYjEWMBQGA1UEAwwNZWxhc3RpY3NlYXJjaDCCAiIwDQYJKoZIhvcN
 AQEBBQADggIPADCCAgoCggIBAMYhP2zPOE3ke9naeK+cIPNV91htuoGGARs+mlY/
@@ -15,22 +15,20 @@ bFMKspGHnytQZF+a+mc5H33G9HiPP3jZE2JjrWlOay+j6ImylMgjcZmHAgaUe3ET
 tyczoQ5/L5BNiyA2h+1TU8jWicNDtl1+CtOsgEVBBHA6p/IHhsHbNZWPrYtIO9mh
 hiJw1R5yrITXnjZY0rObITwyt/e6Sc3YnoQfsSGaLJEG0aDc0RALAhgzj+RY8086
 2RKOyfdw1sw1RmJKdCf+dOzhPyDpvauvCxrL8UZQTzcBs+qpxOWnZFRWeNsLwoDn
-6JXXAgMBAAGjggEmMIIBIjAJBgNVHRMEAjAAMBEGCWCGSAGG+EIBAQQEAwIGQDAz
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-FKFadJx46upif1BrhYZ0iu8o2z8roVCkTjBMMQswCQYDVQQGEwJQVDELMAkGA1UE
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-A1UdJQQMMAoGCCsGAQUFBwMBMA0GCSqGSIb3DQEBCwUAA4ICAQCaABHQxm6mtrM9
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-FKbYFqzgpWksa+zZ2RYYplUAxq0wYw==
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+M8Xe3P1WfqpWZniRmtVi/CWjkPy2JeC6zW4dn7JdkfEFHGsHQZrEZyrVrtVFPRFo
+hbgPGNWCxOhWzg==
 -----END CERTIFICATE-----
diff --git a/spec/fixtures/test_certs/test.p12 b/spec/fixtures/test_certs/test.p12
index 777a235a..2843560c 100644
Binary files a/spec/fixtures/test_certs/test.p12 and b/spec/fixtures/test_certs/test.p12 differ
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