diff --git a/src/Legacy/Cache/APCu.php b/src/Legacy/Cache/APCu.php
index 6e3b26fec..d7e4eb8ed 100644
--- a/src/Legacy/Cache/APCu.php
+++ b/src/Legacy/Cache/APCu.php
@@ -116,7 +116,7 @@ class APCu extends Common
      * @param string|null $name
      * @return bool
      */
-    public function rm(string $name = null): bool
+    public function rm(?string $name = null): bool
     {
         $targetMethod = is_string($name) ? 'delete' : 'flush';
         $name = is_string($name) ? $this->prefix . $name : null;
diff --git a/src/Legacy/Cache/Memcached.php b/src/Legacy/Cache/Memcached.php
index ddbc1b02c..4c5c5225b 100644
--- a/src/Legacy/Cache/Memcached.php
+++ b/src/Legacy/Cache/Memcached.php
@@ -172,7 +172,7 @@ class Memcached extends Common
      * @param string|null $name
      * @return bool
      */
-    public function rm(string $name = null): bool
+    public function rm(?string $name = null): bool
     {
         if (!$this->connected) {
             $this->connect();
diff --git a/src/Legacy/Cache/Redis.php b/src/Legacy/Cache/Redis.php
index d20c53aa8..08a6a16ab 100644
--- a/src/Legacy/Cache/Redis.php
+++ b/src/Legacy/Cache/Redis.php
@@ -174,7 +174,7 @@ class Redis extends Common
      * @param string|null $name
      * @return bool
      */
-    public function rm(string $name = null): bool
+    public function rm(?string $name = null): bool
     {
         if (!$this->connected) {
             $this->connect();
diff --git a/src/Legacy/Cache/Sqlite.php b/src/Legacy/Cache/Sqlite.php
index b6ba7f347..ae38a7699 100644
--- a/src/Legacy/Cache/Sqlite.php
+++ b/src/Legacy/Cache/Sqlite.php
@@ -126,7 +126,7 @@ class Sqlite extends Common
      * @param string|null $name
      * @return bool
      */
-    public function rm(string $name = null): bool
+    public function rm(?string $name = null): bool
     {
         $targetMethod = is_string($name) ? 'delete' : 'flush';
         $name = is_string($name) ? $this->prefix . $name : null;