diff --git a/ClosedXML/ClosedXML/ClosedXML/ClosedXML.csproj b/ClosedXML/ClosedXML/ClosedXML/ClosedXML.csproj
index c0236b7..3f56652 100644
--- a/ClosedXML/ClosedXML/ClosedXML/ClosedXML.csproj
+++ b/ClosedXML/ClosedXML/ClosedXML/ClosedXML.csproj
@@ -233,6 +233,7 @@
     <Compile Include="Excel\Drawings\Style\XLDrawingStyle.cs" />
     <Compile Include="Excel\Drawings\Style\XLDrawingWeb.cs" />
     <Compile Include="Excel\Style\IXLNumberFormatBase.cs" />
+    <Compile Include="Excel\Style\XLStylizedEmpty.cs" />
     <Compile Include="Excel\Tables\XLTableRange.cs" />
     <Compile Include="Excel\Tables\IXLTableRange.cs" />
     <Compile Include="Excel\XLWorkbook_Save.NestedTypes.cs" />
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/Ranges/XLRangeBase.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/Ranges/XLRangeBase.cs
index b3176ab..a08f49c 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/Ranges/XLRangeBase.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/Ranges/XLRangeBase.cs
@@ -1383,14 +1383,7 @@
                 if (canInsert)
                     cellsToInsert.Add(newKey, newCell);
             }
-            //cellsDataValidations.ForEach(kp =>
-            //{
-            //    XLCell targetCell;
-            //    if (!cellsToInsert.TryGetValue(kp.Key, out targetCell))
-            //        targetCell = Worksheet.Cell(kp.Key);
-            //
-            //    targetCell.CopyDataValidation(Worksheet.Cell(kp.Value.SourceAddress), kp.Value.DataValidation);
-            //});
+
 
             cellsToDelete.ForEach(c => Worksheet.Internals.CellsCollection.Remove(c.RowNumber, c.ColumnNumber));
             cellsToInsert.ForEach(
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/Style/XLStylizedEmpty.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/Style/XLStylizedEmpty.cs
new file mode 100644
index 0000000..9e059f9
--- /dev/null
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/Style/XLStylizedEmpty.cs
@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace ClosedXML.Excel
+{
+    internal class XLStylizedEmpty: IXLStylized
+    {
+        public XLStylizedEmpty(IXLStyle defaultStyle)
+        {
+            Style = defaultStyle;
+        }
+        public IXLStyle Style { get; set; }
+        
+        public IEnumerable<IXLStyle> Styles
+        {
+            get
+            {
+                UpdatingStyle = true;
+                yield return Style;
+                UpdatingStyle = false;
+            }
+        }
+
+        public bool UpdatingStyle { get; set; }
+
+        public IXLStyle InnerStyle { get; set; }
+
+        public IXLRanges RangesUsed
+        {
+            get { return new XLRanges(); }
+        }
+
+        public bool StyleChanged { get; set; }
+    }
+}
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
index fc06bce..a4b7dba 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
@@ -111,7 +111,12 @@
             var borders = s.Borders;
             var fonts = s.Fonts;
             Int32 dfCount = 0;
-            var differentialFormats = s.DifferentialFormats.Elements<DifferentialFormat>().ToDictionary(k => dfCount++);
+            Dictionary<Int32, DifferentialFormat> differentialFormats;
+            if (s.DifferentialFormats != null)
+                differentialFormats = s.DifferentialFormats.Elements<DifferentialFormat>().ToDictionary(k => dfCount++);
+            else
+                differentialFormats = new Dictionary<Int32, DifferentialFormat>();
+                
             var sheets = dSpreadsheet.WorkbookPart.Workbook.Sheets;
             Int32 position = 0;
             foreach (Sheet dSheet in sheets.OfType<Sheet>())
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
index 059eb66..8a4d128 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -1824,11 +1824,13 @@
         {
             if (workbookStylesPart.Stylesheet.DifferentialFormats == null)
                 workbookStylesPart.Stylesheet.DifferentialFormats = new DifferentialFormats();
-            else
-                workbookStylesPart.Stylesheet.DifferentialFormats.RemoveAllChildren<DifferentialFormat>();
+            
 
             var differentialFormats = workbookStylesPart.Stylesheet.DifferentialFormats;
 
+            FillDifferentialFormatsCollection(differentialFormats, context.DifferentialFormats);
+
+
             foreach(var ws in Worksheets)
             {
                 foreach(var cf in ws.ConditionalFormats)
@@ -1839,6 +1841,25 @@
             }
 
             differentialFormats.Count = (UInt32) differentialFormats.Count();
+            if (differentialFormats.Count == 0)
+                workbookStylesPart.Stylesheet.DifferentialFormats = null;
+
+        }
+
+        private void FillDifferentialFormatsCollection(DifferentialFormats differentialFormats, Dictionary<IXLStyle, int> dictionary)
+        {
+            dictionary.Clear();
+            Int32 id = 0;
+            foreach(var df in differentialFormats.Elements<DifferentialFormat>())
+            {
+                var style = new XLStyle(new XLStylizedEmpty(DefaultStyle), DefaultStyle);
+                LoadFont(df.Font, style.Font);
+                LoadBorder(df.Border, style.Border);
+                LoadNumberFormat(df.NumberingFormat, style.NumberFormat);
+                LoadFill(df.Fill, style.Fill);
+                if (!dictionary.ContainsKey(style))
+                    dictionary.Add(style, ++id);
+            }
         }
 
         private void AddDifferentialFormat(DifferentialFormats differentialFormats, IXLConditionalFormat cf, SaveContext context)
diff --git a/ClosedXML/ClosedXML/ClosedXML_Net3.5/ClosedXML_Net3.5.csproj b/ClosedXML/ClosedXML/ClosedXML_Net3.5/ClosedXML_Net3.5.csproj
index 926014a..a184d52 100644
--- a/ClosedXML/ClosedXML/ClosedXML_Net3.5/ClosedXML_Net3.5.csproj
+++ b/ClosedXML/ClosedXML/ClosedXML_Net3.5/ClosedXML_Net3.5.csproj
@@ -822,6 +822,7 @@
     <Compile Include="..\ClosedXML\PathHelper.cs">
       <Link>PathHelper.cs</Link>
     </Compile>
+    <Compile Include="Excel\Style\XLStylizedEmpty.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/ClosedXML/ClosedXML/ClosedXML_Net3.5/Excel/Style/XLStylizedEmpty.cs b/ClosedXML/ClosedXML/ClosedXML_Net3.5/Excel/Style/XLStylizedEmpty.cs
new file mode 100644
index 0000000..9e059f9
--- /dev/null
+++ b/ClosedXML/ClosedXML/ClosedXML_Net3.5/Excel/Style/XLStylizedEmpty.cs
@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace ClosedXML.Excel
+{
+    internal class XLStylizedEmpty: IXLStylized
+    {
+        public XLStylizedEmpty(IXLStyle defaultStyle)
+        {
+            Style = defaultStyle;
+        }
+        public IXLStyle Style { get; set; }
+        
+        public IEnumerable<IXLStyle> Styles
+        {
+            get
+            {
+                UpdatingStyle = true;
+                yield return Style;
+                UpdatingStyle = false;
+            }
+        }
+
+        public bool UpdatingStyle { get; set; }
+
+        public IXLStyle InnerStyle { get; set; }
+
+        public IXLRanges RangesUsed
+        {
+            get { return new XLRanges(); }
+        }
+
+        public bool StyleChanged { get; set; }
+    }
+}