diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index 7c7791347d..75bcb8a256 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -89,14 +89,14 @@ jobs:
 
       - name: DotNet Setup
         if: ${{ matrix.options.sdk-preview != true }}
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: |
             8.0.x
 
       - name: DotNet Setup Preview
         if: ${{ matrix.options.sdk-preview == true }}
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: |
             8.0.x
diff --git a/.github/workflows/code-coverage.yml b/.github/workflows/code-coverage.yml
index 7624e86b67..62b6477ee6 100644
--- a/.github/workflows/code-coverage.yml
+++ b/.github/workflows/code-coverage.yml
@@ -55,7 +55,7 @@ jobs:
           restore-keys: ${{ runner.os }}-nuget-
 
       - name: DotNet Setup
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: |
             8.0.x
diff --git a/src/ImageSharp/Formats/Gif/GifEncoderCore.cs b/src/ImageSharp/Formats/Gif/GifEncoderCore.cs
index 9988848d11..1215768e4b 100644
--- a/src/ImageSharp/Formats/Gif/GifEncoderCore.cs
+++ b/src/ImageSharp/Formats/Gif/GifEncoderCore.cs
@@ -103,7 +103,14 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
             {
                 // We avoid dithering by default to preserve the original colors.
                 int transparencyIndex = GetTransparentIndex(quantized, frameMetadata);
-                this.quantizer = new PaletteQuantizer(gifMetadata.GlobalColorTable.Value, new() { Dither = null }, transparencyIndex);
+                if (transparencyIndex >= 0 || gifMetadata.GlobalColorTable.Value.Length < 256)
+                {
+                    this.quantizer = new PaletteQuantizer(gifMetadata.GlobalColorTable.Value, new() { Dither = null }, transparencyIndex);
+                }
+                else
+                {
+                    this.quantizer = KnownQuantizers.Octree;
+                }
             }
             else
             {
@@ -198,19 +205,17 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
     private static GifFrameMetadata GetGifFrameMetadata<TPixel>(ImageFrame<TPixel> frame, int transparencyIndex)
         where TPixel : unmanaged, IPixel<TPixel>
     {
+        GifFrameMetadata? metadata = null;
         if (frame.Metadata.TryGetGifMetadata(out GifFrameMetadata? gif))
         {
-            return (GifFrameMetadata)gif.DeepClone();
+            metadata = (GifFrameMetadata)gif.DeepClone();
         }
-
-        GifFrameMetadata? metadata = null;
-        if (frame.Metadata.TryGetPngMetadata(out PngFrameMetadata? png))
+        else if (frame.Metadata.TryGetPngMetadata(out PngFrameMetadata? png))
         {
             AnimatedImageFrameMetadata ani = png.ToAnimatedImageFrameMetadata();
             metadata = GifFrameMetadata.FromAnimatedMetadata(ani);
         }
-
-        if (frame.Metadata.TryGetWebpFrameMetadata(out WebpFrameMetadata? webp))
+        else if (frame.Metadata.TryGetWebpFrameMetadata(out WebpFrameMetadata? webp))
         {
             AnimatedImageFrameMetadata ani = webp.ToAnimatedImageFrameMetadata();
             metadata = GifFrameMetadata.FromAnimatedMetadata(ani);
diff --git a/src/ImageSharp/Formats/Gif/MetadataExtensions.cs b/src/ImageSharp/Formats/Gif/MetadataExtensions.cs
index 42602f2c78..ad06462e77 100644
--- a/src/ImageSharp/Formats/Gif/MetadataExtensions.cs
+++ b/src/ImageSharp/Formats/Gif/MetadataExtensions.cs
@@ -82,6 +82,9 @@ public static partial class MetadataExtensions
         // has a local palette with 256 colors and is not transparent we should use 'Source'.
         bool blendSource = source.DisposalMethod == GifDisposalMethod.RestoreToBackground || (source.LocalColorTable?.Length == 256 && !source.HasTransparency);
 
+        // If the color table is global and frame has no transparency. Consider it 'Source' also.
+        blendSource |= source.ColorTableMode == GifColorTableMode.Global && !source.HasTransparency;
+
         return new()
         {
             ColorTable = source.LocalColorTable,
diff --git a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
index c81b7eb6cd..e70854b082 100644
--- a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs
@@ -499,7 +499,7 @@ public partial class PngEncoderTests
         // TODO: Find a better way to compare.
         // The image has been visually checked but the quantization pattern used in the png encoder
         // means we cannot use an exact comparison nor replicate using the quantizing processor.
-        ImageComparer.TolerantPercentage(0.46f).VerifySimilarity(output, image);
+        ImageComparer.TolerantPercentage(0.613f).VerifySimilarity(output, image);
 
         GifMetadata gif = image.Metadata.GetGifMetadata();
         PngMetadata png = output.Metadata.GetPngMetadata();
diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs
index b628529028..8aa95d3496 100644
--- a/tests/ImageSharp.Tests/TestImages.cs
+++ b/tests/ImageSharp.Tests/TestImages.cs
@@ -488,6 +488,7 @@ public static class TestImages
         public const string MixedDisposal = "Gif/mixed-disposal.gif";
         public const string M4nb = "Gif/m4nb.gif";
         public const string Bit18RGBCube = "Gif/18-bit_RGB_Cube.gif";
+        public const string Global256NoTrans = "Gif/global-256-no-trans.gif";
 
         // Test images from https://github.com/robert-ancell/pygif/tree/master/test-suite
         public const string ZeroSize = "Gif/image-zero-size.gif";
@@ -535,7 +536,8 @@ public static class TestImages
             Issues.Issue2450_B,
             Issues.BadDescriptorWidth,
             Issues.Issue1530,
-            Bit18RGBCube
+            Bit18RGBCube,
+            Global256NoTrans
         };
     }
 
diff --git a/tests/Images/Input/Gif/global-256-no-trans.gif b/tests/Images/Input/Gif/global-256-no-trans.gif
new file mode 100644
index 0000000000..1afa0d21d7
--- /dev/null
+++ b/tests/Images/Input/Gif/global-256-no-trans.gif
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ce8ed23b4e21328886f5aa7579079123ff6401efdf65e162e565b056ffddab56
+size 669286