diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
index 70dd73b938..9440e51b0f 100644
--- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
@@ -1336,7 +1336,7 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             bitDepth = bits;
         }
 
-        if (Array.IndexOf(PngConstants.ColorTypes[colorType], bitDepth) == -1)
+        if (Array.IndexOf(PngConstants.ColorTypes[colorType], bitDepth) < 0)
         {
             throw new NotSupportedException("Bit depth is not supported or not valid.");
         }