diff --git a/src/Setting/Exception/CollectionEncodingException.php b/src/Setting/Exception/CollectionEncodingException.php
new file mode 100644
index 0000000..6154a00
--- /dev/null
+++ b/src/Setting/Exception/CollectionEncodingException.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * Copyright © OXID eSales AG. All rights reserved.
+ * See LICENSE file for license details.
+ */
+
+declare(strict_types=1);
+
+namespace OxidEsales\GraphQL\ConfigurationAccess\Setting\Exception;
+
+final class CollectionEncodingException extends \Exception
+{
+}
diff --git a/src/Setting/Service/ThemeSettingService.php b/src/Setting/Service/ThemeSettingService.php
index 8548cfe..b16f163 100644
--- a/src/Setting/Service/ThemeSettingService.php
+++ b/src/Setting/Service/ThemeSettingService.php
@@ -9,6 +9,7 @@
 
 namespace OxidEsales\GraphQL\ConfigurationAccess\Setting\Service;
 
+use OxidEsales\GraphQL\ConfigurationAccess\Setting\Exception\CollectionEncodingException;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\Exception\InvalidCollection;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\DataType\IntegerSetting;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\DataType\SettingType;
@@ -57,14 +58,29 @@ public function getSelectSetting(ID $name, string $themeId): StringSetting
 
     public function getCollectionSetting(ID $name, string $themeId): StringSetting
     {
-        $collectionString = $this->themeSettingRepository->getCollection($name, $themeId);
-        return new StringSetting($name, json_encode($collectionString));
+        $collection = $this->themeSettingRepository->getCollection($name, $themeId);
+
+        return new StringSetting($name, $this->jsonEncodeCollection($collection));
     }
 
     public function getAssocCollectionSetting(ID $name, string $themeId): StringSetting
     {
-        $assocCollectionString = $this->themeSettingRepository->getAssocCollection($name, $themeId);
-        return new StringSetting($name, json_encode($assocCollectionString));
+        $assocCollection = $this->themeSettingRepository->getAssocCollection($name, $themeId);
+
+        return new StringSetting($name, $this->jsonEncodeCollection($assocCollection));
+    }
+
+    /**
+     * @throws CollectionEncodingException
+     */
+    private function jsonEncodeCollection(array $collection): string
+    {
+        $jsonValue = json_encode($collection);
+
+        if ($jsonValue === false) {
+            throw new CollectionEncodingException();
+        }
+        return $jsonValue;
     }
 
     /**
diff --git a/tests/Unit/Service/ThemeSettingServiceTest.php b/tests/Unit/Service/ThemeSettingServiceTest.php
index d3b2651..bbd5b6e 100644
--- a/tests/Unit/Service/ThemeSettingServiceTest.php
+++ b/tests/Unit/Service/ThemeSettingServiceTest.php
@@ -3,6 +3,7 @@
 namespace OxidEsales\GraphQL\ConfigurationAccess\Tests\Unit\Service;
 
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\Enum\FieldType;
+use OxidEsales\GraphQL\ConfigurationAccess\Setting\Exception\CollectionEncodingException;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\Exception\InvalidCollection;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\Infrastructure\ThemeSettingRepositoryInterface;
 use OxidEsales\GraphQL\ConfigurationAccess\Setting\Service\ThemeSettingService;
@@ -99,16 +100,18 @@ public function testGetThemeSettingSelect(): void
     public function testGetThemeSettingCollection(): void
     {
         $serviceCollectionSetting = $this->getCollectionSetting();
+        $nameID = new ID('arraySetting');
+        $themeId = 'awesomeTheme';
 
         $repository = $this->createMock(ThemeSettingRepositoryInterface::class);
         $repository->expects($this->once())
             ->method('getCollection')
+            ->with($nameID, $themeId)
             ->willReturn(['nice', 'values']);
 
         $settingService = new ThemeSettingService($repository);
 
-        $nameID = new ID('arraySetting');
-        $collectionSetting = $settingService->getCollectionSetting($nameID, 'awesomeTheme');
+        $collectionSetting = $settingService->getCollectionSetting($nameID, $themeId);
 
         $this->assertEquals($serviceCollectionSetting, $collectionSetting);
     }
@@ -116,20 +119,48 @@ public function testGetThemeSettingCollection(): void
     public function testGetThemeSettingAssocCollection(): void
     {
         $serviceAssocCollectionSetting = $this->getAssocCollectionSetting();
+        $nameID = new ID('aarraySetting');
+        $themeId = 'awesomeTheme';
 
         $repository = $this->createMock(ThemeSettingRepositoryInterface::class);
         $repository->expects($this->once())
             ->method('getAssocCollection')
+            ->with($nameID, $themeId)
             ->willReturn(['first' => '10', 'second' => '20', 'third' => '50']);
 
         $settingService = new ThemeSettingService($repository);
 
-        $nameID = new ID('aarraySetting');
-        $assocCollectionSetting = $settingService->getAssocCollectionSetting($nameID, 'awesomeTheme');
+        $assocCollectionSetting = $settingService->getAssocCollectionSetting($nameID, $themeId);
 
         $this->assertEquals($serviceAssocCollectionSetting, $assocCollectionSetting);
     }
 
+    /** @dataProvider collectionEncodingExceptionDataProvider */
+    public function testCollectionEncodingExceptionThrown(string $repositoryMethod, string $serviceMethod): void
+    {
+        $nameID = new ID('arraySetting');
+        $themeId = 'awesomeTheme';
+        $repositoryResponse = [&$repositoryResponse];
+
+        $repository = $this->createMock(ThemeSettingRepositoryInterface::class);
+        $repository->expects($this->once())
+            ->method($repositoryMethod)
+            ->with($nameID, $themeId)
+            ->willReturn($repositoryResponse);
+
+        $sut = new ThemeSettingService($repository);
+
+        $this->expectException(CollectionEncodingException::class);
+
+        $sut->$serviceMethod($nameID, $themeId);
+    }
+
+    public function collectionEncodingExceptionDataProvider(): \Generator
+    {
+        yield ['repositoryMethod' => 'getCollection', 'serviceMethod' => 'getCollectionSetting'];
+        yield ['repositoryMethod' => 'getAssocCollection', 'serviceMethod' => 'getAssocCollectionSetting'];
+    }
+
     public function testListThemeSettings(): void
     {
         $themeId = 'awesomeTheme';