diff --git a/composer.json b/composer.json
index ed2fa54..5fa0c7b 100644
--- a/composer.json
+++ b/composer.json
@@ -7,8 +7,7 @@
         "symfony/finder": "^3.4 || ^4.0",
         "symfony/yaml": "^3.4 || ^4.0",
         "marcj/topsort": "^1 || ^2",
-        "psr/simple-cache": "^1.0",
-        "silverstripe/framework": "4.13.x-dev"
+        "psr/simple-cache": "^1.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.5",
@@ -21,4 +20,4 @@
             "SilverStripe\\Config\\Tests\\": "tests/"
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Collections/DeltaConfigCollection.php b/src/Collections/DeltaConfigCollection.php
index 7f5e870..b464519 100644
--- a/src/Collections/DeltaConfigCollection.php
+++ b/src/Collections/DeltaConfigCollection.php
@@ -151,7 +151,11 @@ public function isDeltaReset($class = null)
      */
     public function unserialize($serialized)
     {
-        Deprecation::notice('1.6.0', 'Use __unserialize() instead');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.6.0', 'Use __unserialize() instead');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Use __unserialize() instead', E_USER_DEPRECATED);
+        }
         parent::unserialize($serialized);
         $this->postInit();
     }
diff --git a/src/Collections/MemoryConfigCollection.php b/src/Collections/MemoryConfigCollection.php
index 6ffe745..f8211a7 100644
--- a/src/Collections/MemoryConfigCollection.php
+++ b/src/Collections/MemoryConfigCollection.php
@@ -118,7 +118,11 @@ public function checkForDeprecatedConfig($class, $name): void
         $deprecated = $this->getClassConfig('__deprecated', true);
         $data = $deprecated['config'][strtolower($class)][$name] ?? [];
         if (!empty($data)) {
-            Deprecation::notice($data['version'], $data['message'], Deprecation::SCOPE_CONFIG);
+            if (class_exists(Deprecation::class)) {
+                Deprecation::notice($data['version'], $data['message'], Deprecation::SCOPE_CONFIG);
+            } else {
+                user_error($data['message'], E_USER_DEPRECATED);
+            }
         }
     }
 
@@ -216,7 +220,11 @@ public function getAll()
      */
     public function update($class, $name, $value)
     {
-        Deprecation::notice('1.0.0', 'Use merge() instead');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.0.0', 'Use merge() instead');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Use merge() instead', E_USER_DEPRECATED);
+        }
         $this->merge($class, $name, $value);
         return $this;
     }
@@ -229,7 +237,14 @@ public function update($class, $name, $value)
     public function merge($class, $name, $value)
     {
         if (!is_array($value)) {
-            Deprecation::notice('1.12.0', 'Use set() if $value is not an array instead');
+            if (class_exists(Deprecation::class)) {
+                Deprecation::notice('1.12.0', 'Use set() if $value is not an array instead');
+            } else {
+                user_error(
+                    'Non-array values for the $value argument in ' . __METHOD__
+                    . ' are deprecated. Use set() if $value is not an array instead', E_USER_DEPRECATED
+                );
+            }
         }
         // Detect mergeable config
         $existing = $this->get($class, $name, true);
@@ -297,7 +312,11 @@ public function __unserialize(array $data): void
      */
     public function serialize()
     {
-        Deprecation::notice('1.12.0', 'Use __serialize() instead');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.12.0', 'Use __serialize() instead');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Use __serialize() instead', E_USER_DEPRECATED);
+        }
         return serialize($this->__serialize());
     }
 
@@ -311,7 +330,11 @@ public function serialize()
      */
     public function unserialize($serialized)
     {
-        Deprecation::notice('1.12.0', 'Use __unserialize() instead');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.12.0', 'Use __unserialize() instead');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Use __unserialize() instead', E_USER_DEPRECATED);
+        }
         $data = unserialize($serialized ?? '');
         $this->__unserialize($data);
     }
diff --git a/src/Middleware/MiddlewareCommon.php b/src/Middleware/MiddlewareCommon.php
index bbfd279..acc2eb3 100644
--- a/src/Middleware/MiddlewareCommon.php
+++ b/src/Middleware/MiddlewareCommon.php
@@ -75,7 +75,11 @@ public function __unserialize(array $data): void
      */
     public function serialize()
     {
-        Deprecation::notice('1.12.0', 'Will be removed without equivalent functionality to replace it');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.12.0', 'Will be removed without equivalent functionality to replace it');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Will be removed without equivalent functionality to replace it', E_USER_DEPRECATED);
+        }
         return json_encode(array_values($this->__serialize() ?? []));
     }
 
@@ -89,7 +93,11 @@ public function serialize()
      */
     public function unserialize($serialized)
     {
-        Deprecation::notice('1.12.0', 'Will be removed without equivalent functionality to replace it');
+        if (class_exists(Deprecation::class)) {
+            Deprecation::notice('1.12.0', 'Will be removed without equivalent functionality to replace it');
+        } else {
+            user_error(__METHOD__ . ' is deprecated. Will be removed without equivalent functionality to replace it', E_USER_DEPRECATED);
+        }
         $values = json_decode($serialized ?? '', true);
         foreach (array_keys($this->__serialize() ?? []) as $i => $key) {
             if (!property_exists($this, $key ?? '')) {