diff --git a/src/GaugeExporterClient.php b/src/GaugeExporterClient.php
index 485a8b9..7ef4520 100644
--- a/src/GaugeExporterClient.php
+++ b/src/GaugeExporterClient.php
@@ -14,13 +14,13 @@ final class GaugeExporterClient
 {
     private string $apiDomain;
     private ClientInterface $client;
-    private array $defaultLabels;
+    private array $systemLabels;
 
-    public function __construct(ClientInterface $client, string $apiDomain, array $defaultLabels = [])
+    public function __construct(ClientInterface $client, string $apiDomain, array $systemLabels = [])
     {
         $this->client = $client;
         $this->apiDomain = trim($apiDomain, " \n\r\t\v\0/");
-        $this->defaultLabels = MetricLine::normalizeLabels($defaultLabels);
+        $this->systemLabels = MetricLine::normalizeLabels($systemLabels);
     }
 
     /**
@@ -32,6 +32,7 @@ public function send(MetricBag $metricBag, int $ttlSec): void
         $body = [
             'ttl' => $ttlSec,
             'data' => $this->generateData($metricBag),
+            'system_labels' => !empty($this->systemLabels) ? $this->systemLabels : new stdClass(),
         ];
         $request = new Request(
             'PUT',
@@ -50,9 +51,8 @@ private function generateData(MetricBag $metricBag): array
     {
         $result = [];
         foreach ($metricBag->getLogLines() as $logLine) {
-            $labels = array_merge($this->defaultLabels, $logLine->getLabels());
             $result[] = [
-                'labels' => !empty($labels) ? $labels : new stdClass(),
+                'labels' => !empty($logLine->getLabels()) ? $logLine->getLabels() : new stdClass(),
                 'value' => $logLine->getValue()
             ];
         }
diff --git a/tests/GaugeExporterClientTest.php b/tests/GaugeExporterClientTest.php
index 7b85aa5..af73167 100755
--- a/tests/GaugeExporterClientTest.php
+++ b/tests/GaugeExporterClientTest.php
@@ -47,7 +47,7 @@ public function testWholeRequest(): void
             [
                 'method' => 'PUT',
                 'url'  => 'https://example.com/gauge/metric.name',
-                'data' => '{"ttl":100,"data":[{"labels":{"key1":"b","key2":"d"},"value":10},{"labels":{"key1":"b","key2":"e"},"value":10}]}',
+                'data' => '{"ttl":100,"data":[{"labels":{"key1":"b","key2":"d"},"value":10},{"labels":{"key1":"b","key2":"e"},"value":10}],"system_labels":{}}',
             ],
             $this->simplifyRequest($psrClientMock->getLastRequest()),
         );
@@ -69,7 +69,7 @@ public function testWholeRequestWithEmptyLabelsMetric(): void
             [
                 'method' => 'PUT',
                 'url'  => 'https://example.com/gauge/metric.name',
-                'data' => '{"ttl":100,"data":[{"labels":{},"value":10}]}',
+                'data' => '{"ttl":100,"data":[{"labels":{},"value":10}],"system_labels":{}}',
             ],
             $this->simplifyRequest($psrClientMock->getLastRequest()),
         );
@@ -90,13 +90,13 @@ public function testWholeRequestWithEmptyBag(): void
             [
                 'method' => 'PUT',
                 'url'  => 'https://example.com/gauge/metric.name',
-                'data' => '{"ttl":100,"data":[]}',
+                'data' => '{"ttl":100,"data":[],"system_labels":{}}',
             ],
             $this->simplifyRequest($psrClientMock->getLastRequest()),
         );
     }
 
-    public function testWholeRequestWithDefaultLabels(): void
+    public function testWholeRequestWithSystemLabels(): void
     {
         // Arrange
         $psrClientMock = new MockClient();
@@ -117,20 +117,20 @@ public function testWholeRequestWithDefaultLabels(): void
 
         // Assert
         $expectedData = [
-            ['labels' => ['key2' => 'd', 'key3' => 'default_key3', 'key1' => 'b'], 'value' => 10],
-            ['labels' => ['key2' => 'default_key2', 'key3' => 'default_key3', 'key1' => 'b'], 'value' => 12],
+            ['labels' => ['key1' => 'b', 'key2' => 'd'], 'value' => 10],
+            ['labels' => ['key1' => 'b'], 'value' => 12],
         ];
         $this->assertSame(
             [
                 'method' => 'PUT',
                 'url'  => 'https://example.com/gauge/metric.name',
-                'data' => '{"ttl":100,"data":' . json_encode($expectedData) . '}',
+                'data' => '{"ttl":100,"data":' . json_encode($expectedData) . ',"system_labels":{"key2":"default_key2","key3":"default_key3"}}',
             ],
             $this->simplifyRequest($psrClientMock->getLastRequest()),
         );
     }
 
-    public function testWholeRequestWithEmptyBagAndDefaultLabels(): void
+    public function testWholeRequestWithEmptyBagAndSystemLabels(): void
     {
         // Arrange
         $psrClientMock = new MockClient();
@@ -152,7 +152,7 @@ public function testWholeRequestWithEmptyBagAndDefaultLabels(): void
             [
                 'method' => 'PUT',
                 'url'  => 'https://example.com/gauge/metric.name',
-                'data' => '{"ttl":100,"data":[]}',
+                'data' => '{"ttl":100,"data":[],"system_labels":{"key2":"default_key2","key3":"default_key3"}}',
             ],
             $this->simplifyRequest($psrClientMock->getLastRequest()),
         );