diff --git a/composer.json b/composer.json
index d14b292..dc998a3 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
     },
     "optimize-autoloader": true,
     "platform": {
-      "php": "7.4.26"
+      "php": "7.4"
     },
     "sort-packages": true
   },
@@ -28,7 +28,7 @@
     "ext-json": "*",
     "ext-openssl": "*",
     "johnbillion/args": "^1.1",
-    "psr/container": "^2.0.2"
+    "psr/container": "^1.0 || ^2.0"
   },
   "require-dev": {
     "ext-simplexml": "*",
diff --git a/src/Plugin/AbstractContainerProvider.php b/src/Plugin/AbstractContainerProvider.php
index 5d95391..f0518e5 100644
--- a/src/Plugin/AbstractContainerProvider.php
+++ b/src/Plugin/AbstractContainerProvider.php
@@ -2,6 +2,8 @@
 
 namespace TheFrosty\WpUtilities\Plugin;
 
+use Psr\Container\ContainerInterface;
+
 /**
  * Class AbstractContainerProvider
  * @package TheFrosty\WpUtilities\Plugin
@@ -12,13 +14,11 @@ abstract class AbstractContainerProvider implements WpHooksInterface, PluginAwar
 
     /**
      * AbstractContainerProvider constructor.
-     * @param Container|null $container Set the container, or use `$this->setContainer($container)`.
+     * @param Container|ContainerInterface|null $container Set the container, or use `$this->setContainer($container)`.
      */
-    public function __construct(?Container $container = null)
+    public function __construct(?ContainerInterface $container = null)
     {
-        if ($container) {
-            $this->setContainer($container);
-        }
+        $this->setContainer($container);
     }
 
     /**
diff --git a/src/Plugin/Container.php b/src/Plugin/Container.php
index 9474d14..6c3e535 100644
--- a/src/Plugin/Container.php
+++ b/src/Plugin/Container.php
@@ -10,9 +10,9 @@
 
 /**
  * Container class.
- * Extends Pimple to satisfy the ContainerInterface.
+ * Extends Pimple to satisfy the ContainerInterface >= v2.0.0.
+ * @ref https://github.com/php-fig/container/blob/2.0.0/src/ContainerInterface.php
  * @package TheFrosty\WpUtilities\Plugin
- * @SuppressWarnings(PHPMD.ShortVariable)
  */
 class Container extends Pimple implements ContainerInterface
 {
diff --git a/src/Plugin/Container100.php b/src/Plugin/Container100.php
new file mode 100644
index 0000000..071dae3
--- /dev/null
+++ b/src/Plugin/Container100.php
@@ -0,0 +1,47 @@
+<?php declare(strict_types=1);
+
+namespace TheFrosty\WpUtilities\Plugin;
+
+use Pimple\Container as Pimple;
+use Psr\Container\ContainerExceptionInterface;
+use Psr\Container\ContainerInterface;
+use Psr\Container\NotFoundExceptionInterface;
+
+/**
+ * Container100 class.
+ * Extends Pimple to satisfy the ContainerInterface v1.0.0.
+ * @ref https://github.com/php-fig/container/blob/1.0.0/src/ContainerInterface.php
+ * @package TheFrosty\WpUtilities\Plugin
+ */
+class Container100 extends Pimple implements ContainerInterface
+{
+
+    /**
+     * Finds an entry of the container by its identifier and returns it.
+     *
+     * @param string $id Identifier of the entry to look for.
+     *
+     * @return mixed Entry.
+     * @throws ContainerExceptionInterface Error while retrieving the entry.
+     * @throws NotFoundExceptionInterface  No entry was found for **this** identifier.
+     */
+    public function get($id)
+    {
+        return $this->offsetGet($id);
+    }
+
+    /**
+     * Returns true if the container can return an entry for the given identifier.
+     * Returns false otherwise.
+     *
+     * `has($id)` returning true does not mean that `get($id)` will not throw an exception.
+     * It does however mean that `get($id)` will not throw a `NotFoundExceptionInterface`.
+     *
+     * @param string $id Identifier of the entry to look for.
+     * @return bool
+     */
+    public function has($id)
+    {
+        return $this->offsetExists($id);
+    }
+}
diff --git a/src/Plugin/Container110.php b/src/Plugin/Container110.php
new file mode 100644
index 0000000..3cf26c9
--- /dev/null
+++ b/src/Plugin/Container110.php
@@ -0,0 +1,47 @@
+<?php declare(strict_types=1);
+
+namespace TheFrosty\WpUtilities\Plugin;
+
+use Pimple\Container as Pimple;
+use Psr\Container\ContainerExceptionInterface;
+use Psr\Container\ContainerInterface;
+use Psr\Container\NotFoundExceptionInterface;
+
+/**
+ * Container110 class.
+ * Extends Pimple to satisfy the ContainerInterface v1.1.0
+ * @ref https://github.com/php-fig/container/blob/1.1.0/src/ContainerInterface.php.
+ * @package TheFrosty\WpUtilities\Plugin
+ */
+class Container110 extends Pimple implements ContainerInterface
+{
+
+    /**
+     * Finds an entry of the container by its identifier and returns it.
+     *
+     * @param string $id Identifier of the entry to look for.
+     *
+     * @return mixed Entry.
+     * @throws ContainerExceptionInterface Error while retrieving the entry.
+     * @throws NotFoundExceptionInterface  No entry was found for **this** identifier.
+     */
+    public function get(string $id)
+    {
+        return $this->offsetGet($id);
+    }
+
+    /**
+     * Returns true if the container can return an entry for the given identifier.
+     * Returns false otherwise.
+     *
+     * `has($id)` returning true does not mean that `get($id)` will not throw an exception.
+     * It does however mean that `get($id)` will not throw a `NotFoundExceptionInterface`.
+     *
+     * @param string $id Identifier of the entry to look for.
+     * @return bool
+     */
+    public function has(string $id)
+    {
+        return $this->offsetExists($id);
+    }
+}
diff --git a/src/Plugin/ContainerAwareTrait.php b/src/Plugin/ContainerAwareTrait.php
index 6236baa..7c557eb 100644
--- a/src/Plugin/ContainerAwareTrait.php
+++ b/src/Plugin/ContainerAwareTrait.php
@@ -16,10 +16,10 @@ trait ContainerAwareTrait
 {
 
     /**
-     * Container.
-     * @var ContainerInterface
+     * Container instance.
+     * @var ContainerInterface|null
      */
-    private ContainerInterface $container;
+    private ?ContainerInterface $container;
 
     /**
      * Proxy access to container services.
@@ -29,7 +29,7 @@ trait ContainerAwareTrait
      */
     public function __get(string $name)
     {
-        return $this->container->get($name);
+        return $this->container && $this->container->get($name);
     }
 
     /**
@@ -40,7 +40,7 @@ public function __get(string $name)
      */
     public function __isset(string $name): bool
     {
-        return $this->container->has($name);
+        return $this->container && $this->container->has($name);
     }
 
     /**
@@ -53,7 +53,7 @@ public function __isset(string $name): bool
      */
     public function __call(string $method, array $args)
     {
-        if ($this->container->has($method)) {
+        if ($this->container && $this->container->has($method)) {
             $object = $this->container->get($method);
             if (\is_callable($object)) {
                 return \call_user_func_array($object, $args);
@@ -66,9 +66,9 @@ public function __call(string $method, array $args)
     /**
      * Enable access to the DI container by plugin consumers.
      *
-     * @return ContainerInterface
+     * @return ContainerInterface|null
      */
-    public function getContainer(): ContainerInterface
+    public function getContainer(): ?ContainerInterface
     {
         return $this->container;
     }
@@ -76,10 +76,10 @@ public function getContainer(): ContainerInterface
     /**
      * Set the container.
      *
-     * @param ContainerInterface $container Dependency injection container.
+     * @param ContainerInterface|null $container Dependency injection container.
      * @return $this
      */
-    public function setContainer(ContainerInterface $container): self
+    public function setContainer(?ContainerInterface $container = null): self
     {
         $this->container = $container;
 
diff --git a/src/Plugin/PluginFactory.php b/src/Plugin/PluginFactory.php
index a10b2c8..efe7b27 100644
--- a/src/Plugin/PluginFactory.php
+++ b/src/Plugin/PluginFactory.php
@@ -3,6 +3,7 @@
 namespace TheFrosty\WpUtilities\Plugin;
 
 use Psr\Container\ContainerInterface;
+use ReflectionMethod;
 
 /**
  * Class PluginFactory
@@ -34,10 +35,9 @@ public static function getInstance(string $slug): Plugin
      * @param string $slug Plugin slug.
      * @param string|null $filename Optional. Absolute path to the main plugin file.
      *                         This should be passed if the calling file is not the main plugin file.
-     * @param ContainerInterface|null $container
      * @return Plugin A Plugin object instance.
      */
-    public static function create(string $slug, ?string $filename = '', ?ContainerInterface $container = null): Plugin
+    public static function create(string $slug, ?string $filename = ''): Plugin
     {
         if (isset(self::$instances[$slug]) && self::$instances[$slug] instanceof Plugin) {
             return self::$instances[$slug];
@@ -45,7 +45,7 @@ public static function create(string $slug, ?string $filename = '', ?ContainerIn
         // Use the calling file as the main plugin file.
         if (empty($filename)) {
             // @codingStandardsIgnoreStart
-            $backtrace = \debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT, 1);
+            $backtrace = \debug_backtrace(\DEBUG_BACKTRACE_PROVIDE_OBJECT, 1);
             $filename = $backtrace[0]['file'];
             // @codingStandardsIgnoreEnd
         }
@@ -58,7 +58,7 @@ public static function create(string $slug, ?string $filename = '', ?ContainerIn
             ->setSlug($slug)
             ->setUrl(\plugin_dir_url($filename));
 
-        $plugin = self::setContainer($plugin, $container);
+        $plugin = self::setContainer($plugin);
         $plugin->setTemplateLoader(new TemplateLoader($plugin));
         self::$instances[$slug] = $plugin;
 
@@ -69,15 +69,35 @@ public static function create(string $slug, ?string $filename = '', ?ContainerIn
      * Set the Pimple\Container if it's available.
      *
      * @param Plugin $plugin
-     * @param ContainerInterface|null $container
      * @return Plugin
      */
-    private static function setContainer(Plugin $plugin, ?ContainerInterface $container = null): Plugin
+    private static function setContainer(Plugin $plugin): Plugin
     {
-        if (\class_exists('\Pimple\Container') && \interface_exists('\Psr\Container\ContainerInterface')) {
-            $plugin->setContainer($container ?? new Container());
+        if (
+            \class_exists('\Pimple\Container') &&
+            \interface_exists('\Psr\Container\ContainerInterface')
+        ) {
+            $plugin->setContainer(self::getContainer());
         }
 
         return $plugin;
     }
+
+    /**
+     * Return a "Container" stub for ContainerInterface v1.0.0, v1.1.0 and/or >= v2.0.0.
+     * @return ContainerInterface
+     */
+    private static function getContainer(): ContainerInterface
+    {
+        $reflection = new ReflectionMethod('\Psr\Container\ContainerInterface', 'has');
+        if ($reflection->hasReturnType() && $reflection->getReturnType()) {
+            return new Container(); // ContainerInterface >= 2.0.0
+        }
+        $parameter = $reflection->getParameters()[0] ?? null;
+        if ($parameter && $parameter->getType() && $parameter->getType()->getName() === 'string') {
+            return new Container110();
+        }
+
+        return new Container100();
+    }
 }
diff --git a/tests/unit/Plugin/HooksTraitTest.php b/tests/unit/Plugin/HooksTraitTest.php
index 38f53b6..61edc03 100644
--- a/tests/unit/Plugin/HooksTraitTest.php
+++ b/tests/unit/Plugin/HooksTraitTest.php
@@ -19,7 +19,7 @@ public function testRegisterFilters(): void
     {
         $provider = $this->getMockProvider(HookProvider::class);
         $provider->expects($this->exactly(1))
-                 ->method('addFilter')
+                 ->method(self::METHOD_ADD_FILTER)
                  ->will($this->returnCallback(function ($hook, $method, $priority, $arg_count) {
                      TestCase::assertSame('theTitle', $hook);
                      TestCase::assertSame(10, $priority);
@@ -38,7 +38,7 @@ public function testRegisterActions(): void
     {
         $provider = $this->getMockProvider(HookProvider::class);
         $provider->expects($this->exactly(1))
-                 ->method('addFilter')
+                 ->method(self::METHOD_ADD_FILTER)
                  ->will($this->returnCallback(function ($hook, $method, $priority, $arg_count) {
                      TestCase::assertSame('template_redirect', $hook);
                      TestCase::assertSame(10, $priority);
diff --git a/tests/unit/Plugin/PluginAwareTraitTest.php b/tests/unit/Plugin/PluginAwareTraitTest.php
index 708bed4..628997d 100644
--- a/tests/unit/Plugin/PluginAwareTraitTest.php
+++ b/tests/unit/Plugin/PluginAwareTraitTest.php
@@ -2,6 +2,7 @@
 
 namespace TheFrosty\WpUtilities\Tests\Plugin;
 
+use ReflectionClass;
 use TheFrosty\WpUtilities\Plugin\Plugin;
 use TheFrosty\WpUtilities\Plugin\PluginAwareTrait;
 use TheFrosty\WpUtilities\Tests\Plugin\Framework\TestCase;
@@ -15,26 +16,24 @@ class PluginAwareTraitTest extends TestCase
 {
 
     /**
-     * Test set_plugin()
+     * Test setPlugin()
      */
-    public function test_set_plugin()
+    public function testSetPlugin(): void
     {
-        $provider = $this->getMockForTrait(PluginAwareTrait::class);
+        $provider = new class {
 
-        try {
-            $class = new \ReflectionClass($provider);
-            $property = $class->getProperty('plugin');
-            $property->setAccessible(true);
-        } catch (\ReflectionException $exception) {
-            $this->assertInstanceOf(\ReflectionException::class, $exception);
+            use PluginAwareTrait;
+        };
 
-            return;
-        }
+        $class = new ReflectionClass($provider);
+        $property = $class->getProperty('plugin');
+        $property->setAccessible(true);
 
         $plugin = new Plugin();
         /** PluginAwareTrait @var PluginAwareTrait $provider */
         $provider->setPlugin($plugin);
 
         $this->assertSame($plugin, $property->getValue($provider));
+        $this->assertSame($plugin, $provider->getPlugin());
     }
 }
diff --git a/tests/unit/Plugin/PluginRegisterHooksTest.php b/tests/unit/Plugin/PluginRegisterHooksTest.php
index 9060cb6..78448ca 100644
--- a/tests/unit/Plugin/PluginRegisterHooksTest.php
+++ b/tests/unit/Plugin/PluginRegisterHooksTest.php
@@ -2,6 +2,7 @@
 
 namespace TheFrosty\WpUtilities\Tests\Plugin;
 
+use ReflectionClass;
 use TheFrosty\WpUtilities\Plugin\WpHooksInterface;
 use TheFrosty\WpUtilities\Plugin\AbstractHookProvider;
 use TheFrosty\WpUtilities\Plugin\Plugin;
@@ -17,12 +18,12 @@ class PluginRegisterHooksTest extends TestCase
     /**
      * Test AbstractHookProvider
      */
-    public function test_register_hooks(): void
+    public function testRegisterHooks(): void
     {
         $provider = $this->getMockProviderForAbstractClass(AbstractHookProvider::class);
 
         try {
-            $class = new \ReflectionClass($provider);
+            $class = new ReflectionClass($provider);
             $property = $class->getProperty('plugin');
             $property->setAccessible(true);
         } catch (\ReflectionException $exception) {