diff --git a/src/Repository/CustomTypeConverter.php b/src/Repository/CustomTypeConverter.php
index 60a0c54..8fa5b4f 100644
--- a/src/Repository/CustomTypeConverter.php
+++ b/src/Repository/CustomTypeConverter.php
@@ -36,13 +36,15 @@ abstract class CustomTypeConverter
      * @param callable $onCreate
      * @return string
      */
-    public function addOnCreate(callable $onCreate): string
+    public static function addOnCreate(callable $onCreate): string
     {
         $hookKey = null;
-        while (!array_key_exists((string)$hookKey, self::$onCreate) || $hookKey === null) {
+        while (array_key_exists((string)$hookKey, self::$onCreate) || $hookKey === null) {
             $hookKey = Random::generate(12);
         }
 
+        self::$onCreate[$hookKey] = $onCreate;
+
         return $hookKey;
     }
 
@@ -53,7 +55,7 @@ public function addOnCreate(callable $onCreate): string
      * @param string $hookKey
      * @return bool
      */
-    public function removeOnCreate(string $hookKey): bool
+    public static function removeOnCreate(string $hookKey): bool
     {
         if (array_key_exists($hookKey, self::$onCreate)) {
             unset(self::$onCreate[$hookKey]);
diff --git a/tests/Mock/Repository/ConfigurationNotFoundException.php b/tests/Mock/Repository/ConfigurationNotFoundException.php
new file mode 100644
index 0000000..81a4509
--- /dev/null
+++ b/tests/Mock/Repository/ConfigurationNotFoundException.php
@@ -0,0 +1,10 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Mock\Repository;
+
+use Exception;
+
+class ConfigurationNotFoundException extends Exception
+{
+
+}
diff --git a/tests/Mock/Repository/HookExampleConverter.php b/tests/Mock/Repository/HookExampleConverter.php
new file mode 100644
index 0000000..23ddbf0
--- /dev/null
+++ b/tests/Mock/Repository/HookExampleConverter.php
@@ -0,0 +1,46 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Mock\Repository;
+
+use Exception;
+use stdClass;
+use Zrnik\MkSQL\Repository\CustomTypeConverter;
+
+class HookExampleConverter extends CustomTypeConverter
+{
+    public ?stdClass $configuration = null;
+
+    public function serialize(mixed $value): string|bool
+    {
+        /** @noinspection JsonEncodingApiUsageInspection */
+        $encoded = json_encode($value);
+
+        if($this->configuration === null) {
+            throw new ConfigurationNotFoundException('Configuration not found!');
+        }
+
+
+        if($encoded === false) {
+            throw new Exception('Should not be false!');
+        }
+
+        return $encoded;
+    }
+
+    public function deserialize(mixed $value): mixed
+    {
+        /** @noinspection JsonEncodingApiUsageInspection */
+        $decoded = json_decode($value, true);
+
+        if($this->configuration === null) {
+            throw new ConfigurationNotFoundException('Configuration not found!');
+        }
+
+        return $decoded;
+    }
+
+    public function getDatabaseType(): string
+    {
+        return 'longtext';
+    }
+}
diff --git a/tests/Repository/CustomTypeConverterTest.php b/tests/Repository/CustomTypeConverterTest.php
new file mode 100644
index 0000000..310c2da
--- /dev/null
+++ b/tests/Repository/CustomTypeConverterTest.php
@@ -0,0 +1,63 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Repository;
+
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+use stdClass;
+use Tests\Mock\Repository\ConfigurationNotFoundException;
+use Tests\Mock\Repository\HookExampleConverter;
+use Zrnik\MkSQL\Repository\CustomTypeConverter;
+use Zrnik\PHPUnit\Exceptions;
+
+class CustomTypeConverterTest extends TestCase
+{
+    use Exceptions;
+
+    public string $testProperty;
+
+    public function testHook(): void
+    {
+        $thisReflection = new ReflectionClass($this);
+
+        /** @var HookExampleConverter $converter */
+        $converter = CustomTypeConverter::initialize(
+            HookExampleConverter::class, $thisReflection->getProperty('testProperty')
+        );
+
+        $exampleArray = ['hello', 'world'];
+
+        $this->assertExceptionThrown(
+            ConfigurationNotFoundException::class,
+            function () use ($converter, $exampleArray) {
+                $converter->serialize($exampleArray);
+            }
+        );
+
+        CustomTypeConverter::addOnCreate(
+            static function (CustomTypeConverter $converter) {
+                if($converter instanceof HookExampleConverter) {
+                    $converter->configuration = new stdClass();
+                }
+            }
+        );
+
+        //Re-create the converter, so the hook has a chance to get applied:
+
+        /** @var HookExampleConverter $converter */
+        $converter = CustomTypeConverter::initialize(
+            HookExampleConverter::class, $thisReflection->getProperty('testProperty')
+        );
+
+
+        $this->assertNoExceptionThrown(
+            function () use ($converter, $exampleArray) {
+                $converter->serialize($exampleArray);
+            }
+        );
+
+
+    }
+
+
+}