diff --git a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs
index d4c35a1ad..dda5f751c 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs
@@ -56,6 +56,12 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs
             where TPixel : unmanaged, ImageSharp.PixelFormats.IPixel<TPixel>
         {
             var bmpReadDefines = new BmpReadDefines
+            {
+                // See https://github.com/SixLabors/ImageSharp/issues/1380
+                // Validation fails on Ubuntu despite identical header generation
+                // on all platforms.
+                IgnoreFileSize = !TestEnvironment.IsWindows
+            };
             {
                 IgnoreFileSize = true
             };