diff --git a/src/Encoders/FileExtensionEncoder.php b/src/Encoders/FileExtensionEncoder.php
index 9db37ed5..9736112f 100644
--- a/src/Encoders/FileExtensionEncoder.php
+++ b/src/Encoders/FileExtensionEncoder.php
@@ -61,7 +61,7 @@ class FileExtensionEncoder extends AutoEncoder
         }
 
         try {
-            $extension = is_string($extension) ? FileExtension::from($extension) : $extension;
+            $extension = is_string($extension) ? FileExtension::from(strtolower($extension)) : $extension;
         } catch (Error) {
             throw new EncoderException('No encoder found for file extension (' . $extension . ').');
         }
diff --git a/tests/Unit/Encoders/FileExtensionEncoderTest.php b/tests/Unit/Encoders/FileExtensionEncoderTest.php
index ac03cf92..d44597be 100644
--- a/tests/Unit/Encoders/FileExtensionEncoderTest.php
+++ b/tests/Unit/Encoders/FileExtensionEncoderTest.php
@@ -67,6 +67,17 @@ final class FileExtensionEncoderTest extends BaseTestCase
         yield ['tif', TiffEncoder::class];
         yield ['jp2', Jpeg2000Encoder::class];
         yield ['heic', HeicEncoder::class];
+        yield ['WEBP', WebpEncoder::class];
+        yield ['AVIF', AvifEncoder::class];
+        yield ['JPEG', JpegEncoder::class];
+        yield ['JPG', JpegEncoder::class];
+        yield ['BMP', BmpEncoder::class];
+        yield ['GIF', GifEncoder::class];
+        yield ['PNG', PngEncoder::class];
+        yield ['TIFF', TiffEncoder::class];
+        yield ['TIF', TiffEncoder::class];
+        yield ['JP2', Jpeg2000Encoder::class];
+        yield ['HEIC', HeicEncoder::class];
         yield [FileExtension::WEBP, WebpEncoder::class];
         yield [FileExtension::AVIF, AvifEncoder::class];
         yield [FileExtension::JPG, JpegEncoder::class];