diff --git a/source/Sylvan.Data.Excel/Xlsb/XlsbDataWriter.cs b/source/Sylvan.Data.Excel/Xlsb/XlsbDataWriter.cs
index 218f2f0..f89b8b9 100644
--- a/source/Sylvan.Data.Excel/Xlsb/XlsbDataWriter.cs
+++ b/source/Sylvan.Data.Excel/Xlsb/XlsbDataWriter.cs
@@ -544,7 +544,7 @@ async Task<WriteResult> WriteInternal(DbDataReader data, string? worksheetName,
 		bw.Write(0);
 		bw.Write(0);
 		bw.Write(0);
-		bw.Write(fieldCount);
+		bw.Write(fieldCount - 1);
 		bw.WriteMarker(RecordType.FilterEnd);