diff --git a/src/Serializer/PrometheusEncoder.php b/src/Serializer/PrometheusEncoder.php
index 44ba6d4..cca5f51 100644
--- a/src/Serializer/PrometheusEncoder.php
+++ b/src/Serializer/PrometheusEncoder.php
@@ -47,7 +47,7 @@ protected function encodeLabels(array $labels) {
     }
     $output = [];
     foreach ($labels as $key => $value) {
-      $output[] = $key . '="' . $value . '"';
+      $output[] = $key . '="' . $this->escapeValue($value) . '"';
     }
     return '{' . implode(',', $output) . '}';
   }