diff --git a/BulkCommand.php b/BulkCommand.php
index aa78d78c..86d16b4a 100644
--- a/BulkCommand.php
+++ b/BulkCommand.php
@@ -72,9 +72,17 @@ public function execute()
             $body = '{}';
         } elseif (is_array($this->actions)) {
             $body = '';
+            $prettyPrintSupported = property_exists('yii\\helpers\\Json', 'prettyPrint');
+            if ($prettyPrintSupported) {
+                $originalPrettyPrint = Json::$prettyPrint;
+                Json::$prettyPrint = false; // ElasticSearch bulk API uses new lines as delimiters.
+            }
             foreach ($this->actions as $action) {
                 $body .= Json::encode($action) . "\n";
             }
+            if ($prettyPrintSupported) {
+                Json::$prettyPrint = $originalPrettyPrint;
+            }
         } else {
             $body = $this->actions;
         }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5e78001d..e390a862 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,7 @@ Yii Framework 2 Elasticsearch extension Change Log
 2.1.5 under development
 -----------------------
 
-- no changes in this release.
+- Bug #344: Disabled JSON pretty print for ElasticSearch bulk API (rhertogh)
 
 
 2.1.4 May 22, 2023