diff --git a/src/EPPlus/Core/Worksheet/WorksheetCopyHelper.cs b/src/EPPlus/Core/Worksheet/WorksheetCopyHelper.cs
index 824d37cd1..65d1ff596 100644
--- a/src/EPPlus/Core/Worksheet/WorksheetCopyHelper.cs
+++ b/src/EPPlus/Core/Worksheet/WorksheetCopyHelper.cs
@@ -63,7 +63,7 @@ internal static ExcelWorksheet Copy(ExcelWorksheets worksheets, string name, Exc
             string relID = worksheets.CreateWorkbookRel(name, sheetID, uriWorksheet, false, null);
 
             ExcelWorksheet added = new ExcelWorksheet(nsm, pck, relID, uriWorksheet, name, sheetID, worksheets.Count + pck._worksheetAdd, eWorkSheetHidden.Visible);
-
+            added.SetNewUid();
             //Copy comments
             if (copy.ThreadedComments.Count > 0)
             {
diff --git a/src/EPPlus/Encryption/EncryptionHandler.cs b/src/EPPlus/Encryption/EncryptionHandler.cs
index 170b5ffc9..e57be397c 100644
--- a/src/EPPlus/Encryption/EncryptionHandler.cs
+++ b/src/EPPlus/Encryption/EncryptionHandler.cs
@@ -198,11 +198,7 @@ private MemoryStream EncryptPackageAgile(byte[] package, ExcelEncryption encrypt
         private byte[] EncryptDataAgile(byte[] data, EncryptionInfoAgile encryptionInfo, HashAlgorithm hashProvider)
         {
             var ke = encryptionInfo.KeyEncryptors[0];
-#if Core
             var aes = Aes.Create();
-#else
-            RijndaelManaged aes = new RijndaelManaged();
-#endif
             aes.KeySize = ke.KeyBits;
             aes.Mode = CipherMode.CBC;
             aes.Padding = PaddingMode.Zeros;
@@ -472,11 +468,7 @@ private EncryptionInfoBinary CreateEncryptionInfo(string password, AlgorithmID a
         }
         private byte[] EncryptData(byte[] key, byte[] data, bool useDataSize)
         {
-#if (Core)
             var aes = Aes.Create();
-#else
-            RijndaelManaged aes = new RijndaelManaged();
-#endif
             aes.KeySize = key.Length * 8;
             aes.Mode = CipherMode.ECB;
             aes.Padding = PaddingMode.Zeros;
@@ -673,11 +665,7 @@ private MemoryStream DecryptBinary(EncryptionInfoBinary encryptionInfo, string p
                 encryptionInfo.Header.AlgID == AlgorithmID.AES256
                 )
             {
-#if (Core)
                 var decryptKey = Aes.Create();
-#else
-            RijndaelManaged decryptKey = new RijndaelManaged();
-#endif
                 decryptKey.KeySize = encryptionInfo.Header.KeySize;
                 decryptKey.Mode = CipherMode.ECB;
                 decryptKey.Padding = PaddingMode.None;
@@ -716,11 +704,7 @@ private MemoryStream DecryptBinary(EncryptionInfoBinary encryptionInfo, string p
         /// <returns></returns>
         private bool IsPasswordValid(byte[] key, EncryptionInfoBinary encryptionInfo)
         {
-#if (Core)
             var decryptKey = Aes.Create();
-#else
-                RijndaelManaged decryptKey = new RijndaelManaged();
-#endif
             decryptKey.KeySize = encryptionInfo.Header.KeySize;
             decryptKey.Mode = CipherMode.ECB;
             decryptKey.Padding = PaddingMode.None;
@@ -845,7 +829,7 @@ private SymmetricAlgorithm GetEncryptionAlgorithm(EncryptionInfoAgile.Encryption
             switch (encr.CipherAlgorithm)
             {
                 case eCipherAlgorithm.AES:
-                    return new RijndaelManaged();
+                    return Aes.Create();
                 case eCipherAlgorithm.DES:
                     return new DESCryptoServiceProvider();
                 case eCipherAlgorithm.TRIPLE_DES:
diff --git a/src/EPPlus/ExcelWorksheet.cs b/src/EPPlus/ExcelWorksheet.cs
index a3cc1b962..9351ed923 100644
--- a/src/EPPlus/ExcelWorksheet.cs
+++ b/src/EPPlus/ExcelWorksheet.cs
@@ -1238,7 +1238,10 @@ private void CreateVmlCollection()
                 }
             }
         }
-
+        internal void SetNewUid()
+        {
+            SetXmlNodeString("@xr:uid", "{" + Guid.NewGuid().ToString().ToUpperInvariant() + "}");
+        }
         private void CreateXml()
         {
             _worksheetXml = new XmlDocument();
diff --git a/src/EPPlusTest/Issues.cs b/src/EPPlusTest/Issues.cs
index 0fa8e40d9..b72ad52d4 100644
--- a/src/EPPlusTest/Issues.cs
+++ b/src/EPPlusTest/Issues.cs
@@ -5016,5 +5016,16 @@ public void I892()
                 SaveAndCleanup(p);
             }
         }
+        [TestMethod]
+        public void SaveDialogIssue890()
+        {
+            using (var package = OpenTemplatePackage("issue890.xlsx"))
+            {
+                ExcelWorksheet worksheet = package.Workbook.Worksheets[0];
+                ExcelWorksheet newWorksheet = package.Workbook.Worksheets.Add("Sheet2", worksheet);
+                SaveAndCleanup(package);
+            }
+        }
+
     }
 }
\ No newline at end of file