diff --git a/src/View/Helper/PosterHelper.php b/src/View/Helper/PosterHelper.php
index 658c718..2719068 100644
--- a/src/View/Helper/PosterHelper.php
+++ b/src/View/Helper/PosterHelper.php
@@ -165,9 +165,9 @@ public function sourceSet(ObjectEntity|null $object, array|string|false $thumbOp
         }
 
         $url = $this->url($variant, $thumbOptions, $posterOptions);
-        $width = $this->getStreamWidth($variant);
+        $slotWidth = $this->getSlotWidth($variant);
 
-        return sprintf('%s %sw, %s %sw', $url, $width, $fallbackUrl, $fallbackWidth);
+        return sprintf('%s %sw, %s %sw', $url, $slotWidth, $fallbackUrl, $fallbackWidth);
     }
 
     /**
@@ -182,6 +182,17 @@ protected function getStreamWidth(Media $media): int
         return Hash::get($media, 'streams.0.width', $this->getConfig('PosterMobile.slotWidth', static::MOBILE_DEFAULT_WIDTH));
     }
 
+    /**
+     * Get the slot width of a media object.
+     * 
+     * @param \BEdita\Core\Model\Entity\Media $variant Media entity.
+     * @return int
+     */
+    protected function getSlotWidth(Media $variant): int 
+    {
+        return Hash::get($variant ?? [], '_joinData.params.slot_width', $this->getConfig('PosterMobile.slotWidth', static::MOBILE_DEFAULT_WIDTH));
+    }
+
     /**
      * Get sizes attribute for image.
      *
@@ -192,7 +203,7 @@ public function sizes(Media $poster): string
     {
         $variant = $this->mobile($poster);
         $maxWidth = $this->getConfig('PosterMobile.maxWidth', static::MOBILE_MAX_WIDTH);
-        $slotWidth = Hash::get($variant ?? [], '_joinData.params.slot_width', $this->getConfig('PosterMobile.slotWidth', static::MOBILE_DEFAULT_WIDTH));
+        $slotWidth = $this->getSlotWidth($variant);
 
         return sprintf('(max-width: %spx) %spx', $maxWidth, $slotWidth);
     }
diff --git a/tests/TestCase/View/Helper/PosterHelperTest.php b/tests/TestCase/View/Helper/PosterHelperTest.php
index 0468ec5..d8df78d 100644
--- a/tests/TestCase/View/Helper/PosterHelperTest.php
+++ b/tests/TestCase/View/Helper/PosterHelperTest.php
@@ -204,7 +204,7 @@ public function testSourceSet()
         // no variant
         $this->assertSame('https://www.bedita.com/first.png 1500w', $this->Poster->sourceSet($image));
 
-        $this->setVariantProviderThumbnail($image, 640, 480);
+        $this->setVariantProviderThumbnail($image, 2000, 480);
 
         // variant available
         $this->assertSame('https://www.bedita.com/favicon.png 640w, https://www.bedita.com/first.png 1500w', $this->Poster->sourceSet($image));
@@ -219,7 +219,7 @@ public function testSourceSet()
     public function testSizes()
     {
         $image = $this->createImage(1500, 1000);
-        $this->setVariantProviderThumbnail($image, 640, 480);
+        $this->setVariantProviderThumbnail($image, 2000, 480);
 
         // no slot_width set, using image width
         $this->assertSame('(max-width: 767px) 640px', $this->Poster->sizes($image));