diff --git a/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs b/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
index 96ab92f25c..697ee0f981 100644
--- a/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
@@ -10,7 +10,7 @@ namespace ImageSharp.Formats
     /// <summary>
     /// Detects bmp file headers
     /// </summary>
-    internal class BmpImageFormatDetector : IImageFormatDetector
+    public sealed class BmpImageFormatDetector : IImageFormatDetector
     {
         /// <inheritdoc/>
         public int HeaderSize => 2;
diff --git a/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs b/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
index 5a6dfe1988..04fcfc516c 100644
--- a/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
@@ -10,7 +10,7 @@ namespace ImageSharp.Formats
     /// <summary>
     /// Detects gif file headers
     /// </summary>
-    public class GifImageFormatDetector : IImageFormatDetector
+    public sealed class GifImageFormatDetector : IImageFormatDetector
     {
         /// <inheritdoc/>
         public int HeaderSize => 6;
diff --git a/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs b/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
index 8d6923c8de..b72b290c04 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
@@ -10,7 +10,7 @@ namespace ImageSharp.Formats
     /// <summary>
     /// Detects Jpeg file headers
     /// </summary>
-    public class JpegImageFormatDetector : IImageFormatDetector
+    public sealed class JpegImageFormatDetector : IImageFormatDetector
     {
         /// <inheritdoc/>
         public int HeaderSize => 11;
diff --git a/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs b/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
index a9327983be..fdea3eb8ae 100644
--- a/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
@@ -10,7 +10,7 @@ namespace ImageSharp.Formats
     /// <summary>
     /// Detects png file headers
     /// </summary>
-    public class PngImageFormatDetector : IImageFormatDetector
+    public sealed class PngImageFormatDetector : IImageFormatDetector
     {
         /// <inheritdoc/>
         public int HeaderSize => 8;