diff --git a/src/Normalizer/IconNormalizer.php b/src/Normalizer/IconNormalizer.php
index b591849..5787f95 100644
--- a/src/Normalizer/IconNormalizer.php
+++ b/src/Normalizer/IconNormalizer.php
@@ -6,7 +6,6 @@
 
 use SpomkyLabs\PwaBundle\Dto\Icon;
 use Symfony\Component\AssetMapper\AssetMapperInterface;
-use Symfony\Component\AssetMapper\MappedAsset;
 use Symfony\Component\Mime\MimeTypes;
 use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
 use function assert;
@@ -33,7 +32,7 @@ public function normalize(mixed $object, string $format = null, array $context =
         if ($url === null) {
             $url = $object->src;
         }
-        $format = $this->getFormat($object, $asset);
+        $format = $this->getFormat($object, $asset === null ? $object->src : $asset->sourcePath);
 
         $result = [
             'src' => $url,
@@ -65,17 +64,16 @@ public function getSupportedTypes(?string $format): array
         ];
     }
 
-    private function getFormat(Icon $object, ?MappedAsset $asset): ?string
+    private function getFormat(Icon $object, string $sourcePath): ?string
     {
         if ($object->format !== null) {
             return $object->format;
         }
 
-        if ($asset === null || ! class_exists(MimeTypes::class)) {
+        if (! file_exists($sourcePath) || ! class_exists(MimeTypes::class)) {
             return null;
         }
 
-        $mime = MimeTypes::getDefault();
-        return $mime->guessMimeType($asset->sourcePath);
+        return MimeTypes::getDefault()->guessMimeType($sourcePath);
     }
 }
diff --git a/src/Normalizer/ScreenshotNormalizer.php b/src/Normalizer/ScreenshotNormalizer.php
index 22ef59f..d97238f 100644
--- a/src/Normalizer/ScreenshotNormalizer.php
+++ b/src/Normalizer/ScreenshotNormalizer.php
@@ -36,7 +36,7 @@ public function normalize(mixed $object, string $format = null, array $context =
             $url = $object->src;
         }
         ['sizes' => $sizes, 'formFactor' => $formFactor] = $this->getSizes($object, $asset);
-        $format = $this->getFormat($object, $asset);
+        $format = $this->getFormat($object, $asset === null ? $object->src : $asset->sourcePath);
 
         $result = [
             'src' => $url,
@@ -98,18 +98,17 @@ private function getSizes(Screenshot $object, null|MappedAsset $asset): array
         ];
     }
 
-    private function getFormat(Screenshot $object, ?MappedAsset $asset): ?string
+    private function getFormat(Screenshot $object, string $sourcePath): ?string
     {
         if ($object->format !== null) {
             return $object->format;
         }
 
-        if ($this->imageProcessor === null || $asset === null || ! class_exists(MimeTypes::class)) {
+        if (! file_exists($sourcePath) || ! class_exists(MimeTypes::class)) {
             return null;
         }
 
-        $mime = MimeTypes::getDefault();
-        return $mime->guessMimeType($asset->sourcePath);
+        return MimeTypes::getDefault()->guessMimeType($sourcePath);
     }
 
     private function getFormFactor(?int $width, ?int $height): ?string