diff --git a/components/fpspreadsheet/examples/other/test_virtualmode.lpi b/components/fpspreadsheet/examples/other/test_virtualmode.lpi
index dae3987f6..f88cb3f45 100644
--- a/components/fpspreadsheet/examples/other/test_virtualmode.lpi
+++ b/components/fpspreadsheet/examples/other/test_virtualmode.lpi
@@ -78,6 +78,7 @@
     <Linking>
       <Debugging>
         <DebugInfoType Value="dsDwarf2Set"/>
+        <UseHeaptrc Value="True"/>
       </Debugging>
     </Linking>
   </CompilerOptions>
diff --git a/components/fpspreadsheet/examples/other/test_virtualmode.lpr b/components/fpspreadsheet/examples/other/test_virtualmode.lpr
index bb8b00d2e..ca67c8108 100644
--- a/components/fpspreadsheet/examples/other/test_virtualmode.lpr
+++ b/components/fpspreadsheet/examples/other/test_virtualmode.lpr
@@ -7,7 +7,7 @@ uses
   cthreads,
   {$ENDIF}{$ENDIF}
   Classes, laz_fpspreadsheet,
-  { you can add units after this }
+  { you can add units after this }    lazutf8,
   SysUtils, variants, fpspreadsheet, xlsbiff2, xlsbiff5, xlsbiff8, xlsxooxml;
 
 type
@@ -41,12 +41,11 @@ var
       // This makes the style of the "headerTemplate" cell available to
       // formatting of all virtual cells in row 0.
       // Important: The template cell must be an existing cell in the worksheet.
-    end else    {
-    if odd(random(10)) then }begin
-      s := Format('R=%d-C=%d', [ARow, ACol]);
-      AData := s;
-    end {else
-      AData := 10000*ARow + ACol};
+    end else
+    if odd(random(10)) then begin
+      AData := Format('R=%d-C=%d', [ARow, ACol]);
+    end else
+      AData := 10000*ARow + ACol;
 
     // you can use the OnNeedData also to provide feedback on how the process
     // progresses:
@@ -65,8 +64,8 @@ begin
 
       { These are the essential commands to activate virtual mode: }
 
-      workbook.WritingOptions := [woVirtualMode, woBufStream];
-//      workbook.WritingOptions := [woVirtualMode];
+//      workbook.WritingOptions := [woVirtualMode, woBufStream];
+      workbook.WritingOptions := [woVirtualMode];
       { woBufStream can be omitted, but is important for large files: it causes
         writing temporary data to a buffered file stream instead of a pure
         memory stream which can overflow memory. The option can slow down the
@@ -75,7 +74,7 @@ begin
       { Next two numbers define the size of virtual spreadsheet.
         In case of a database, VirtualRowCount is the RecordCount, VirtualColCount
         the number of fields to be written to the spreadsheet file }
-      workbook.VirtualRowCount := 60000;
+      workbook.VirtualRowCount := 20000;
       workbook.VirtualColCount := 100;
 
       { The event handler for OnNeedCellData links the workbook to the method
@@ -96,19 +95,20 @@ begin
       { In case of a database, you would open the dataset before calling this: }
 
       t := Now;
-      workbook.WriteToFile('test_virtual.xlsx', sfOOXML, true);
-      //workbook.WriteToFile('test_virtual.xls', sfExcel8, true);
+      //workbook.WriteToFile('test_virtual.xlsx', sfOOXML, true);
+      workbook.WriteToFile('test_virtual.xls', sfExcel8, true);
       t := Now - t;
 
     finally
       workbook.Free;
     end;
 
-    WriteLn(Format('Execution time: %.3f sec', [t*24*60*60]));
-    WriteLn('Press [ENTER] to quit...');
-    ReadLn;
   finally
     dataprovider.Free;
   end;
+
+  WriteLn(Format('Execution time: %.3f sec', [t*24*60*60]));
+  WriteLn('Press [ENTER] to quit...');
+  ReadLn;
 end.
 
diff --git a/components/fpspreadsheet/fpspreadsheet.pas b/components/fpspreadsheet/fpspreadsheet.pas
index d6b3e1837..121e68d28 100755
--- a/components/fpspreadsheet/fpspreadsheet.pas
+++ b/components/fpspreadsheet/fpspreadsheet.pas
@@ -1072,6 +1072,9 @@ function GetFileFormatName(AFormat: TsSpreadsheetFormat): String;
 procedure MakeLEPalette(APalette: PsPalette; APaletteSize: Integer);
 function SameCellBorders(ACell1, ACell2: PCell): Boolean;
 
+procedure InitCell(var ACell: TCell);
+
+
 implementation
 
 uses
@@ -1460,6 +1463,47 @@ begin
   end;
 end;
 
+{@@
+  Initalizes a new cell
+}
+procedure InitCell(var ACell: TCell);
+begin
+  ACell.RPNFormulaValue := nil;
+  ACell.FormulaValue.FormulaStr := '';
+  ACell.UTF8StringValue := '';
+  ACell.NumberFormatStr := '';
+  FillChar(ACell, SizeOf(ACell), 0);
+end;
+(*
+      Col: Cardinal; // zero-based
+    Row: Cardinal; // zero-based
+    ContentType: TCellContentType;
+    { Possible values for the cells }
+    FormulaValue: TsFormula;
+    RPNFormulaValue: TsRPNFormula;
+    NumberValue: double;
+    UTF8StringValue: ansistring;
+    DateTimeValue: TDateTime;
+    BoolValue: Boolean;
+    ErrorValue: TsErrorValue;
+    { Formatting fields }
+    { When adding/deleting formatting fields don't forget to update CopyFormat! }
+    UsedFormattingFields: TsUsedFormattingFields;
+    FontIndex: Integer;
+    TextRotation: TsTextRotation;
+    HorAlignment: TsHorAlignment;
+    VertAlignment: TsVertAlignment;
+    Border: TsCellBorders;
+    BorderStyles: TsCelLBorderStyles;
+    BackgroundColor: TsColor;
+    NumberFormat: TsNumberFormat;
+    NumberFormatStr: String;
+    RGBBackgroundColor: TFPColor; // only valid if BackgroundColor=scRGBCOLOR
+    { Status flags }
+    CalcState: TsCalcState;
+  *)
+
+
 { TsWorksheet }
 
 {@@
@@ -5803,6 +5847,7 @@ end;
 function NewRPNItem: PRPNItem;
 begin
   Result := GetMem(SizeOf(TRPNItem));
+  Result^.FE.StringValue := '';
   FillChar(Result^.FE, SizeOf(Result^.FE), 0);
   Result^.FE.StringValue := '';
 end;
diff --git a/components/fpspreadsheet/xlscommon.pas b/components/fpspreadsheet/xlscommon.pas
index 1796e3daa..c1b41a463 100644
--- a/components/fpspreadsheet/xlscommon.pas
+++ b/components/fpspreadsheet/xlscommon.pas
@@ -2577,7 +2577,8 @@ var
 begin
   for r := 0 to Workbook.VirtualRowCount-1 do begin
     for c := 0 to Workbook.VirtualColCount-1 do begin
-      FillChar(lCell, SizeOf(lCell), 0);
+      InitCell(lCell);
+//      FillChar(lCell, SizeOf(lCell), 0);
       value := varNull;
       styleCell := nil;
       Workbook.OnNeedCellData(Workbook, r, c, value, styleCell);
@@ -2607,6 +2608,7 @@ begin
       end else
         lCell.ContentType := cctEmpty;
       WriteCellCallback(@lCell, AStream);
+      value := varNULL;
     end;
   end;
 end;
diff --git a/components/fpspreadsheet/xlsxooxml.pas b/components/fpspreadsheet/xlsxooxml.pas
index 25b35c972..5c0bceaee 100755
--- a/components/fpspreadsheet/xlsxooxml.pas
+++ b/components/fpspreadsheet/xlsxooxml.pas
@@ -249,12 +249,12 @@ begin
   SetLength(FFormattingStyles, 2);
 
   // Default style
-  FillChar(FFormattingStyles[0], SizeOf(TCell), 0);
+  InitCell(FFormattingStyles[0]);
   FFormattingStyles[0].BorderStyles := DEFAULT_BORDERSTYLES;
   FFormattingStyles[0].Row := 0;
 
   // Bold style
-  FillChar(FFormattingStyles[1], SizeOf(TCell), 0);
+  InitCell(FFormattingStyles[1]);
   FFormattingStyles[1].UsedFormattingFields := [uffBold];
   FFormattingStyles[1].FontIndex := 1;  // this is the "bold" font
   FFormattingStyles[1].Row := 1;
@@ -917,7 +917,8 @@ begin
       AppendToStream(FSSheets[FCurSheetNum], Format(
         '<row r="%d" spans="1:%d"%s>', [r+1, Workbook.VirtualColCount, rh]));
       for c := 0 to Workbook.VirtualColCount-1 do begin
-        FillChar(lCell, SizeOf(lCell), 0);
+        //FillChar(lCell, SizeOf(lCell), 0);
+        InitCell(lCell);
         CellPosText := CurSheet.CellPosToText(r, c);
         value := varNull;
         styleCell := nil;
@@ -948,6 +949,7 @@ begin
           lCell.BoolValue := value <> 0;
         end;
         WriteCellCallback(@lCell, FSSheets[FCurSheetNum]);
+        varClear(value);
       end;
       AppendToStream(FSSheets[FCurSheetNum],
         '</row>');