diff --git a/src/Plugin/PdfBackend/LocalServerPdfBackend.php b/src/Plugin/PdfBackend/LocalServerPdfBackend.php
index fc16ad141b962a4f1c7d1d584bbf613fd77ac212..30f889638fbbd11d881e2e3e60e348600d51f277 100644
--- a/src/Plugin/PdfBackend/LocalServerPdfBackend.php
+++ b/src/Plugin/PdfBackend/LocalServerPdfBackend.php
@@ -10,9 +10,8 @@ use Drupal\fillpdf\FieldMapping\TextFieldMapping;
 use Drupal\fillpdf\Plugin\PdfBackendBase;
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\RequestException;
+use GuzzleHttp\Utils;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use function GuzzleHttp\json_decode;
-use function GuzzleHttp\json_encode;
 
 /**
  * LocalServer PdfBackend plugin.
@@ -85,7 +84,7 @@ class LocalServerPdfBackend extends PdfBackendBase implements ContainerFactoryPl
       'pdf' => base64_encode($pdf_content),
     ];
 
-    $json = json_encode($request);
+    $json = Utils::jsonEncode($request);
 
     $fields = [];
 
@@ -107,7 +106,7 @@ class LocalServerPdfBackend extends PdfBackendBase implements ContainerFactoryPl
       }
     }
 
-    $fields = json_decode((string) $fields_response->getBody(), TRUE);
+    $fields = Utils::jsonDecode((string) $fields_response->getBody(), TRUE);
 
     return $fields;
   }
@@ -158,7 +157,7 @@ class LocalServerPdfBackend extends PdfBackendBase implements ContainerFactoryPl
       'fields' => $api_fields,
     ];
 
-    $json = json_encode($request);
+    $json = Utils::jsonEncode($request);
 
     try {
       $response = $this->httpClient->post($this->configuration['local_service_endpoint'] . '/api/v1/merge', [
@@ -166,7 +165,7 @@ class LocalServerPdfBackend extends PdfBackendBase implements ContainerFactoryPl
         'headers' => ['Content-Type' => 'application/json'],
       ]);
 
-      $decoded = json_decode((string) $response->getBody(), TRUE);
+      $decoded = Utils::jsonDecode((string) $response->getBody(), TRUE);
       return base64_decode($decoded['pdf']);
     }
     catch (RequestException $e) {