diff --git a/composer.json b/composer.json
index f2f8b90..5f8aaf8 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
         "jimdo/prometheus_client_php": "*"
     },
     "require": {
-        "php": "^7.2",
+        "php": "^7.2||^8.0",
         "ext-json": "*",
         "guzzlehttp/guzzle": "^6.3",
         "symfony/polyfill-apcu": "^1.6"
diff --git a/src/Prometheus/RenderTextFormat.php b/src/Prometheus/RenderTextFormat.php
index a5b78dc..a314a60 100644
--- a/src/Prometheus/RenderTextFormat.php
+++ b/src/Prometheus/RenderTextFormat.php
@@ -56,9 +56,9 @@ private function renderSample(MetricFamilySamples $metric, Sample $sample): stri
      */
     private function escapeLabelValue($v): string
     {
-        $v = str_replace("\\", "\\\\", $v);
-        $v = str_replace("\n", "\\n", $v);
-        $v = str_replace("\"", "\\\"", $v);
+        $v = str_replace("\\", "\\\\", $v ? (string)$v : '');
+        $v = str_replace("\n", "\\n", $v ? (string)$v : '');
+        $v = str_replace("\"", "\\\"", $v ? (string)$v : '');
         return $v;
     }
 }