diff --git a/ClosedXML/Excel/XLWorkbook_Load.cs b/ClosedXML/Excel/XLWorkbook_Load.cs
index da58c0b..7641a16 100644
--- a/ClosedXML/Excel/XLWorkbook_Load.cs
+++ b/ClosedXML/Excel/XLWorkbook_Load.cs
@@ -68,7 +68,7 @@
             SetProperties(dSpreadsheet);
 
             SharedStringItem[] sharedStrings = null;
-            if (dSpreadsheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().Count() > 0)
+            if (dSpreadsheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().Any())
             {
                 var shareStringPart = dSpreadsheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().First();
                 sharedStrings = shareStringPart.SharedStringTable.Elements<SharedStringItem>().ToArray();
diff --git a/ClosedXML/Utils/XmlEncoder.cs b/ClosedXML/Utils/XmlEncoder.cs
index 4219901..3177a12 100644
--- a/ClosedXML/Utils/XmlEncoder.cs
+++ b/ClosedXML/Utils/XmlEncoder.cs
@@ -1,10 +1,13 @@
 using System.Text;
+using System.Text.RegularExpressions;
 using System.Xml;
 
 namespace ClosedXML.Utils
 {
     public static class XmlEncoder
     {
+        private static readonly Regex xHHHHRegex = new Regex("_(x[\\dA-F]{4})_", RegexOptions.Compiled);
+
         /// <summary>
         /// Checks if a character is not allowed to the XML Spec http://www.w3.org/TR/REC-xml/#charsets
         /// </summary>
@@ -23,20 +26,23 @@
         {
             if (encodeStr == null) return null;
 
-            var newString = new StringBuilder();
+            encodeStr = xHHHHRegex.Replace(encodeStr, "_x005F_$1_");
+
+            var sb = new StringBuilder(encodeStr.Length);
 
             foreach (var ch in encodeStr)
             {
                 if (IsXmlChar(ch)) //this method is new in .NET 4
                 {
-                    newString.Append(ch);
+                    sb.Append(ch);
                 }
                 else
                 {
-                    newString.Append(XmlConvert.EncodeName(ch.ToString()));
+                    sb.Append(XmlConvert.EncodeName(ch.ToString()));
                 }
             }
-            return newString.ToString();
+
+            return sb.ToString();
         }
 
         public static string DecodeString(string decodeStr)
diff --git a/ClosedXML_Tests/Excel/Saving/SavingTests.cs b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
index 60a1d7a..70b4b3d 100644
--- a/ClosedXML_Tests/Excel/Saving/SavingTests.cs
+++ b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
@@ -2,6 +2,7 @@
 using NUnit.Framework;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Threading;
 
 namespace ClosedXML_Tests.Excel.Saving
@@ -34,11 +35,32 @@
         }
 
         [Test]
+        public void CanEscape_xHHHH_Correctly()
+        {
+            using (var ms = new MemoryStream())
+            {
+                using (var wb = new XLWorkbook())
+                {
+                    var ws = wb.AddWorksheet("Sheet1");
+                    ws.FirstCell().Value = "Reserve_TT_A_BLOCAGE_CAG_x6904_2";
+                    wb.SaveAs(ms);
+                }
+
+                ms.Seek(0, SeekOrigin.Begin);
+
+                using (var wb = new XLWorkbook(ms))
+                {
+                    var ws = wb.Worksheets.First();
+                    Assert.AreEqual("Reserve_TT_A_BLOCAGE_CAG_x6904_2", ws.FirstCell().Value);
+                }
+            }
+        }
+
+        [Test]
         public void CanSaveFileMultipleTimesAfterDeletingWorksheet()
         {
             // https://github.com/ClosedXML/ClosedXML/issues/435
 
-
             using (var ms = new MemoryStream())
             {
                 using (XLWorkbook book1 = new XLWorkbook())
@@ -61,7 +83,6 @@
             }
         }
 
-
         [Test]
         public void CanSaveAndValidateFileInAnotherCulture()
         {