diff --git a/source/helpers.pas b/source/helpers.pas
index b5a88bb1..a64f7675 100644
--- a/source/helpers.pas
+++ b/source/helpers.pas
@@ -1841,13 +1841,16 @@ end;
 }
 function FormatNumber( str: String ): String; Overload;
 var
-  i, p: Integer;
+  i, p, Left: Integer;
 begin
   Result := str;
   Result := StringReplace(Result, '.', DecimalSeparator, [rfReplaceAll]);
   p := Pos(DecimalSeparator, Result);
   if p = 0 then p := Length(Result)+1;
-  if p > 0 then for i:=p-1 downto 2 do begin
+  Left := 2;
+  if (Length(Result) >= 1) and (Result[1] = '-') then
+    Left := 3; 
+  if p > 0 then for i:=p-1 downto Left do begin
     if (p-i) mod 3 = 0 then
       Insert(ThousandSeparator, Result, i);
   end;