diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 6cedc78f98..3a59abe14b 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -11304,12 +11304,6 @@ parameters:
 			count: 1
 			path: src/lib/FieldType/Image/ImageStorage/Gateway/DoctrineStorage.php
 
-		-
-			message: '#^Method Ibexa\\Core\\FieldType\\Image\\ImageThumbnailProxyStrategy\:\:getThumbnail\(\) never returns null so it can be removed from the return type\.$#'
-			identifier: return.unusedType
-			count: 1
-			path: src/lib/FieldType/Image/ImageThumbnailProxyStrategy.php
-
 		-
 			message: '#^Parameter \#3 \$pad_string of function str_pad expects string, int given\.$#'
 			identifier: argument.type
diff --git a/src/lib/FieldType/Image/ImageThumbnailProxyStrategy.php b/src/lib/FieldType/Image/ImageThumbnailProxyStrategy.php
index eac301a992..ed363f34b4 100644
--- a/src/lib/FieldType/Image/ImageThumbnailProxyStrategy.php
+++ b/src/lib/FieldType/Image/ImageThumbnailProxyStrategy.php
@@ -14,14 +14,13 @@
 use Ibexa\Contracts\Core\Repository\Values\Content\VersionInfo;
 use Ibexa\Core\Repository\ProxyFactory\ProxyGeneratorInterface;
 use ProxyManager\Proxy\LazyLoadingInterface;
+use RuntimeException;
 
 final class ImageThumbnailProxyStrategy implements FieldTypeBasedThumbnailStrategy
 {
-    /** @var \Ibexa\Core\FieldType\Image\ImageThumbnailStrategy */
-    private $imageThumbnailStrategy;
+    private ImageThumbnailStrategy $imageThumbnailStrategy;
 
-    /** @var \Ibexa\Core\Repository\ProxyFactory\ProxyGeneratorInterface */
-    private $proxyGenerator;
+    private ProxyGeneratorInterface $proxyGenerator;
 
     public function __construct(
         ImageThumbnailStrategy $imageThumbnailStrategy,
@@ -36,7 +35,7 @@ public function getFieldTypeIdentifier(): string
         return $this->imageThumbnailStrategy->getFieldTypeIdentifier();
     }
 
-    public function getThumbnail(Field $field, ?VersionInfo $versionInfo = null): ?Thumbnail
+    public function getThumbnail(Field $field, ?VersionInfo $versionInfo = null): Thumbnail
     {
         $initializer = function (
             &$wrappedObject,
@@ -49,6 +48,15 @@ public function getThumbnail(Field $field, ?VersionInfo $versionInfo = null): ?T
 
             $wrappedObject = $this->imageThumbnailStrategy->getThumbnail($field, $versionInfo);
 
+            if ($wrappedObject === null) {
+                throw new RuntimeException(sprintf(
+                    'Failed to prepare thumbnail for field type "%s" (ID: %s) using "%s" strategy.',
+                    $field->getId(),
+                    $field->getFieldTypeIdentifier(),
+                    get_debug_type($this->imageThumbnailStrategy),
+                ));
+            }
+
             return true;
         };
 
diff --git a/tests/bundle/IO/FieldType/Image/ImageThumbnailProxyStrategyTest.php b/tests/bundle/IO/FieldType/Image/ImageThumbnailProxyStrategyTest.php
new file mode 100644
index 0000000000..0a9a468a89
--- /dev/null
+++ b/tests/bundle/IO/FieldType/Image/ImageThumbnailProxyStrategyTest.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+namespace Ibexa\Tests\Bundle\IO\FieldType\Image;
+
+use Ibexa\Contracts\Core\Repository\Values\Content\Field;
+use Ibexa\Contracts\Core\Repository\Values\Content\VersionInfo;
+use Ibexa\Core\FieldType\Image\ImageThumbnailProxyStrategy;
+use Ibexa\Core\FieldType\Image\ImageThumbnailStrategy;
+use Ibexa\Core\Repository\ProxyFactory\ProxyGenerator;
+use Ibexa\Core\Repository\ProxyFactory\ProxyGeneratorInterface;
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+
+final class ImageThumbnailProxyStrategyTest extends TestCase
+{
+    /** @var \Ibexa\Core\FieldType\Image\ImageThumbnailStrategy&\PHPUnit\Framework\MockObject\MockObject */
+    private ImageThumbnailStrategy $imageThumbnailStrategyMock;
+
+    private ProxyGeneratorInterface $proxyGeneratorMock;
+
+    private ImageThumbnailProxyStrategy $strategy;
+
+    protected function setUp(): void
+    {
+        $this->imageThumbnailStrategyMock = $this->createMock(ImageThumbnailStrategy::class);
+        $this->proxyGeneratorMock = new ProxyGenerator(__DIR__ . '/../../../../../var/proxy');
+
+        $this->strategy = new ImageThumbnailProxyStrategy(
+            $this->imageThumbnailStrategyMock,
+            $this->proxyGeneratorMock,
+        );
+    }
+
+    public function testGetThumbnailThrowsExceptionIfWrappedObjectIsNull(): void
+    {
+        $field = $this->createMock(Field::class);
+        $field->method('getId')->willReturn(123);
+        $field->method('getFieldTypeIdentifier')->willReturn('ezimage');
+
+        $versionInfo = $this->createMock(VersionInfo::class);
+
+        $this->imageThumbnailStrategyMock
+            ->expects(self::once())
+            ->method('getThumbnail')
+            ->with($field, $versionInfo)
+            ->willReturn(null);
+
+        $thumbnail = $this->strategy->getThumbnail($field, $versionInfo);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Failed to prepare thumbnail for field type "123" (ID: ezimage) using');
+
+        // Initialize proxy
+        // @phpstan-ignore expr.resultUnused
+        $thumbnail->mimeType;
+    }
+}