diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index d04eaef..99e1730 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -3376,6 +3376,11 @@
             AddDifferentialFormats(workbookStylesPart, context);
         }
 
+        /// <summary>
+        /// Populates the differential formats that are currently in the file to the SaveContext
+        /// </summary>
+        /// <param name="workbookStylesPart">The workbook styles part.</param>
+        /// <param name="context">The context.</param>
         private void AddDifferentialFormats(WorkbookStylesPart workbookStylesPart, SaveContext context)
         {
             if (workbookStylesPart.Stylesheet.DifferentialFormats == null)
@@ -3915,7 +3920,9 @@
                                 break;
 
                             case XLColorType.Indexed:
-                                backgroundColor.Indexed = (UInt32)fillInfo.Fill.BackgroundColor.Indexed;
+                                // 64 is 'transparent' and should be ignored for differential formats
+                                if (fillInfo.Fill.BackgroundColor.Indexed != 64)
+                                    backgroundColor.Indexed = (UInt32)fillInfo.Fill.BackgroundColor.Indexed;
                                 break;
 
                             case XLColorType.Theme: