diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index a547d98..edde683 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -3680,6 +3680,15 @@
             if (b.DiagonalDown != null)
                 nb.DiagonalDown = b.DiagonalDown.Value;
 
+            if (b.DiagonalBorder != null)
+            {
+                if (b.DiagonalBorder.Style != null)
+                    nb.DiagonalBorder = b.DiagonalBorder.Style.Value.ToClosedXml();
+                var bColor = GetColor(b.DiagonalBorder.Color);
+                if (bColor.HasValue)
+                    nb.DiagonalBorderColor = bColor;
+            }
+
             if (b.LeftBorder != null)
             {
                 if (b.LeftBorder.Style != null)
diff --git a/ClosedXML_Tests/Resource/Examples/Styles/StyleBorder.xlsx b/ClosedXML_Tests/Resource/Examples/Styles/StyleBorder.xlsx
index 4d52bd6..bc01898 100644
--- a/ClosedXML_Tests/Resource/Examples/Styles/StyleBorder.xlsx
+++ b/ClosedXML_Tests/Resource/Examples/Styles/StyleBorder.xlsx
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