diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 8451e51..4c0831a 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -2547,7 +2547,7 @@
                 var df = new DataField
                 {
                     Name = value.CustomName,
-                    Field = (UInt32)sourceColumn.ColumnNumber() - 1,
+                    Field = (UInt32)(sourceColumn.ColumnNumber() - pt.SourceRange.RangeAddress.FirstAddress.ColumnNumber),
                     Subtotal = value.SummaryFormula.ToOpenXml(),
                     ShowDataAs = value.Calculation.ToOpenXml(),
                     NumberFormatId = numberFormatId