diff --git a/composer.json b/composer.json
index 89850b13..85b1477b 100644
--- a/composer.json
+++ b/composer.json
@@ -16,8 +16,7 @@
     },
     "require": {
         "php": "^7.2|^8.0",
-        "ext-json": "*",
-        "symfony/polyfill-apcu": "^1.6"
+        "ext-json": "*"
     },
     "require-dev": {
         "guzzlehttp/guzzle": "^6.3|^7.0",
@@ -26,12 +25,14 @@
         "phpstan/phpstan-phpunit": "^0.12.16",
         "phpstan/phpstan-strict-rules": "^0.12.5",
         "phpunit/phpunit": "^8.4|^9.4",
-        "squizlabs/php_codesniffer": "^3.5"
+        "squizlabs/php_codesniffer": "^3.5",
+        "symfony/polyfill-apcu": "^1.6"
     },
     "suggest": {
         "ext-redis": "Required if using Redis.",
         "ext-apc": "Required if using APCu.",
-        "promphp/prometheus_push_gateway_php": "An easy client for using Prometheus PushGateway."
+        "promphp/prometheus_push_gateway_php": "An easy client for using Prometheus PushGateway.",
+        "symfony/polyfill-apcu": "Required if you use APCu on PHP8.0+"
     },
     "autoload": {
         "psr-4": {
diff --git a/src/Prometheus/Storage/Redis.php b/src/Prometheus/Storage/Redis.php
index d05ef8f4..19d0110f 100644
--- a/src/Prometheus/Storage/Redis.php
+++ b/src/Prometheus/Storage/Redis.php
@@ -285,7 +285,7 @@ public function updateSummary(array $data): void
         if (false === $json) {
             throw new RuntimeException(json_last_error_msg());
         }
-        $this->redis->setnx($metaKey, $json);
+        $this->redis->setNx($metaKey, $json);
 
         // store value key
         $valueKey = $summaryKey . ':' . $this->valueKey($data);
@@ -293,7 +293,7 @@ public function updateSummary(array $data): void
         if (false === $json) {
             throw new RuntimeException(json_last_error_msg());
         }
-        $this->redis->setnx($valueKey, $json);
+        $this->redis->setNx($valueKey, $json);
 
         // trick to handle uniqid collision
         $done = false;