From 9fbc8ed3df4c61a9e248865af3d758e222435c16 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Thu, 22 Nov 2018 17:12:43 +0000
Subject: [PATCH] Use existing field

---
 src/ImageSharp/Formats/Png/PngEncoderCore.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
index 8a31aaf51b..bb800c8a48 100644
--- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
@@ -785,7 +785,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             else if (pngMetaData.ColorType.Equals(PngColorType.Grayscale))
             {
                 Span<byte> alpha = this.buffer.AsSpan();
-                if (pngMetaData.TransparentGray16.HasValue && this.bitDepth == 16)
+                if (pngMetaData.TransparentGray16.HasValue && this.use16Bit)
                 {
                     BinaryPrimitives.WriteUInt16LittleEndian(alpha, pngMetaData.TransparentGray16.Value.PackedValue);
                     this.WriteChunk(stream, PngChunkType.Transparency, this.buffer, 0, 2);