diff --git a/composer.json b/composer.json
index 4e5da58..86d9f9f 100644
--- a/composer.json
+++ b/composer.json
@@ -29,7 +29,7 @@
         "ext-mbstring": "*",
         "laminas/laminas-math": "^3.4",
         "laminas/laminas-stdlib": "^3.8",
-        "psr/container": "^1.1"
+        "psr/container": "^1.1 || ^2.0"
     },
     "require-dev": {
         "laminas/laminas-coding-standard": "~2.5.0",
diff --git a/src/Symmetric/PaddingPluginManager.php b/src/Symmetric/PaddingPluginManager.php
index b41f990..9f7c158 100644
--- a/src/Symmetric/PaddingPluginManager.php
+++ b/src/Symmetric/PaddingPluginManager.php
@@ -16,7 +16,7 @@
  * Padding\PaddingInterface. Additionally, it registers a number of default
  * padding adapters available.
  */
-class PaddingPluginManager implements ContainerInterface
+final class PaddingPluginManager implements ContainerInterface
 {
     /** @var array<string, string> */
     private array $paddings = [
@@ -27,11 +27,8 @@ class PaddingPluginManager implements ContainerInterface
 
     /**
      * Do we have the padding plugin?
-     *
-     * @param  string $id
-     * @return bool
      */
-    public function has($id)
+    public function has(string $id): bool
     {
         return array_key_exists($id, $this->paddings);
     }
@@ -39,10 +36,9 @@ public function has($id)
     /**
      * Retrieve the padding plugin
      *
-     * @param  string $id
      * @return Padding\PaddingInterface
      */
-    public function get($id)
+    public function get(string $id)
     {
         if (! $this->has($id)) {
             throw new Exception\NotFoundException(sprintf(
diff --git a/src/SymmetricPluginManager.php b/src/SymmetricPluginManager.php
index 450a7a3..0aff79c 100644
--- a/src/SymmetricPluginManager.php
+++ b/src/SymmetricPluginManager.php
@@ -16,7 +16,7 @@
  * Symmetric\SymmetricInterface. Additionally, it registers a number of default
  * symmetric adapters available.
  */
-class SymmetricPluginManager implements ContainerInterface
+final class SymmetricPluginManager implements ContainerInterface
 {
     /**
      * Default set of symmetric adapters
@@ -30,11 +30,8 @@ class SymmetricPluginManager implements ContainerInterface
 
     /**
      * Do we have the symmetric plugin?
-     *
-     * @param  string $id
-     * @return bool
      */
-    public function has($id)
+    public function has(string $id): bool
     {
         return array_key_exists($id, $this->symmetric);
     }
@@ -42,10 +39,9 @@ public function has($id)
     /**
      * Retrieve the symmetric plugin
      *
-     * @param  string $id
      * @return Symmetric\SymmetricInterface
      */
-    public function get($id)
+    public function get(string $id)
     {
         if (! $this->has($id)) {
             throw new Exception\NotFoundException(sprintf(