diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 3d839de..1544814 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -334,14 +334,19 @@
                 GenerateThemePartContent(themePart);
             }
 
+            // Custom properties
             if (CustomProperties.Any())
             {
-                document.GetPartsOfType<CustomFilePropertiesPart>().ToList().ForEach(p => document.DeletePart(p));
                 var customFilePropertiesPart =
-                    document.AddNewPart<CustomFilePropertiesPart>(context.RelIdGenerator.GetNext(RelType.Workbook));
+                    document.CustomFilePropertiesPart ?? document.AddNewPart<CustomFilePropertiesPart>(context.RelIdGenerator.GetNext(RelType.Workbook));
 
                 GenerateCustomFilePropertiesPartContent(customFilePropertiesPart);
             }
+            else
+            {
+                if (document.CustomFilePropertiesPart != null)
+                    document.DeletePart(document.CustomFilePropertiesPart);
+            }
             SetPackageProperties(document);
 
             // Clear list of deleted worksheets to prevent errors on multiple saves
@@ -1749,10 +1754,10 @@
             themePart.Theme = theme1;
         }
 
-        private void GenerateCustomFilePropertiesPartContent(CustomFilePropertiesPart customFilePropertiesPart1)
+        private void GenerateCustomFilePropertiesPartContent(CustomFilePropertiesPart customFilePropertiesPart)
         {
-            var properties2 = new DocumentFormat.OpenXml.CustomProperties.Properties();
-            properties2.AddNamespaceDeclaration("vt",
+            var properties = new DocumentFormat.OpenXml.CustomProperties.Properties();
+            properties.AddNamespaceDeclaration("vt",
                 "http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes");
             var propertyId = 1;
             foreach (var p in CustomProperties)
@@ -1792,10 +1797,10 @@
                     var vTBool1 = new VTBool { Text = p.GetValue<Boolean>().ToString().ToLower() };
                     customDocumentProperty.AppendChild(vTBool1);
                 }
-                properties2.AppendChild(customDocumentProperty);
+                properties.AppendChild(customDocumentProperty);
             }
 
-            customFilePropertiesPart1.Properties = properties2;
+            customFilePropertiesPart.Properties = properties;
         }
 
         private void SetPackageProperties(OpenXmlPackage document)
diff --git a/ClosedXML_Tests/Resource/Examples/Misc/WorkbookProperties.xlsx b/ClosedXML_Tests/Resource/Examples/Misc/WorkbookProperties.xlsx
index d9fba2c..969d71b 100644
--- a/ClosedXML_Tests/Resource/Examples/Misc/WorkbookProperties.xlsx
+++ b/ClosedXML_Tests/Resource/Examples/Misc/WorkbookProperties.xlsx
Binary files differ
diff --git a/ClosedXML_Tests/Resource/Other/PivotTableReferenceFiles/PivotTableWithNoneTheme/outputfile.xlsx b/ClosedXML_Tests/Resource/Other/PivotTableReferenceFiles/PivotTableWithNoneTheme/outputfile.xlsx
index be50146..309b880 100644
--- a/ClosedXML_Tests/Resource/Other/PivotTableReferenceFiles/PivotTableWithNoneTheme/outputfile.xlsx
+++ b/ClosedXML_Tests/Resource/Other/PivotTableReferenceFiles/PivotTableWithNoneTheme/outputfile.xlsx
Binary files differ
diff --git a/ClosedXML_Tests/Resource/Other/StyleReferenceFiles/TransparentBackgroundFill/TransparentBackgroundFill.xlsx b/ClosedXML_Tests/Resource/Other/StyleReferenceFiles/TransparentBackgroundFill/TransparentBackgroundFill.xlsx
index 6953f33..8619a59 100644
--- a/ClosedXML_Tests/Resource/Other/StyleReferenceFiles/TransparentBackgroundFill/TransparentBackgroundFill.xlsx
+++ b/ClosedXML_Tests/Resource/Other/StyleReferenceFiles/TransparentBackgroundFill/TransparentBackgroundFill.xlsx
Binary files differ