diff --git a/components/tachart/tacustomseries.pas b/components/tachart/tacustomseries.pas
index d47470f18e..49e781ac17 100644
--- a/components/tachart/tacustomseries.pas
+++ b/components/tachart/tacustomseries.pas
@@ -40,7 +40,7 @@ type
     procedure SetAxisIndexY(AValue: Integer);
 
   protected
-    procedure GetGraphBounds(out ABounds: TDoubleRect); override;
+    procedure GetGraphBounds(var ABounds: TDoubleRect); override;
     procedure SetActive(AValue: Boolean); override;
     procedure SetDepth(AValue: TChartDistance); override;
     procedure SetShowInLegend(AValue: Boolean); override;
@@ -96,7 +96,7 @@ type
     procedure AfterDraw; override;
     procedure BeforeDraw; override;
     function ColorOrDefault(AColor: TColor; ADefault: TColor = clTAColor): TColor;
-    procedure GetBounds(out ABounds: TDoubleRect); override;
+    procedure GetBounds(var ABounds: TDoubleRect); override;
     function GetGraphPoint(AIndex: Integer): TDoublePoint;
     function GetGraphPointX(AIndex: Integer): Double; inline;
     function GetGraphPointY(AIndex: Integer): Double; inline;
@@ -170,7 +170,7 @@ begin
   FAxisIndexY := DEF_AXIS_INDEX;
 end;
 
-procedure TCustomChartSeries.GetGraphBounds(out ABounds: TDoubleRect);
+procedure TCustomChartSeries.GetGraphBounds(var ABounds: TDoubleRect);
 begin
   GetBounds(ABounds);
   with ABounds do begin
@@ -379,7 +379,7 @@ begin
     Result := Source.FormatItem(Marks.Format, AIndex);
 end;
 
-procedure TChartSeries.GetBounds(out ABounds: TDoubleRect);
+procedure TChartSeries.GetBounds(var ABounds: TDoubleRect);
 begin
   if not Active or (Count = 0) then exit;
   ABounds := Extent;
diff --git a/components/tachart/tagraph.pas b/components/tachart/tagraph.pas
index 639d8260c9..d11d625d00 100644
--- a/components/tachart/tagraph.pas
+++ b/components/tachart/tagraph.pas
@@ -55,8 +55,10 @@ type
     procedure AfterAdd; virtual;
     procedure AfterDraw; virtual;
     procedure BeforeDraw; virtual;
-    procedure GetBounds(out ABounds: TDoubleRect); virtual; abstract;
-    procedure GetGraphBounds(out ABounds: TDoubleRect); virtual; abstract;
+    // Set series bounds in axis coordinates.
+    // Some or all bounds may be left unset, in which case they will be ignored.
+    procedure GetBounds(var ABounds: TDoubleRect); virtual; abstract;
+    procedure GetGraphBounds(var ABounds: TDoubleRect); virtual; abstract;
     procedure GetLegendItems(AItems: TChartLegendItems); virtual; abstract;
     procedure SetActive(AValue: Boolean); virtual; abstract;
     procedure SetDepth(AValue: TChartDistance); virtual; abstract;
diff --git a/components/tachart/taseries.pas b/components/tachart/taseries.pas
index 2e4ff5f1b2..3f27a67194 100644
--- a/components/tachart/taseries.pas
+++ b/components/tachart/taseries.pas
@@ -232,7 +232,7 @@ type
     procedure SetSeriesColor(AValue: TColor);
     procedure SetUseBounds(AValue: Boolean);
   protected
-    procedure GetBounds(out ABounds: TDoubleRect); override;
+    procedure GetBounds(var ABounds: TDoubleRect); override;
     procedure GetLegendItems(AItems: TChartLegendItems); override;
   public
     constructor Create(AOwner: TComponent); override;
@@ -273,7 +273,7 @@ type
     procedure SetPen(const AValue: TChartPen);
     procedure SetStep(AValue: TFuncSeriesStep);
   protected
-    procedure GetBounds(out ABounds: TDoubleRect); override;
+    procedure GetBounds(var ABounds: TDoubleRect); override;
     procedure GetLegendItems(AItems: TChartLegendItems); override;
 
   public
@@ -296,7 +296,7 @@ type
   end;
 
   TSeriesDrawEvent = procedure (ACanvas: TCanvas; const ARect: TRect) of object;
-  TSeriesGetBoundsEvent = procedure (out ABounds: TDoubleRect) of object;
+  TSeriesGetBoundsEvent = procedure (var ABounds: TDoubleRect) of object;
 
   { TUserDrawnSeries }
 
@@ -307,7 +307,7 @@ type
     procedure SetOnDraw(AValue: TSeriesDrawEvent);
     procedure SetOnGetBounds(AValue: TSeriesGetBoundsEvent);
   protected
-    procedure GetBounds(out ABounds: TDoubleRect); override;
+    procedure GetBounds(var ABounds: TDoubleRect); override;
     procedure GetLegendItems(AItems: TChartLegendItems); override;
   public
     procedure Draw(ACanvas: TCanvas); override;
@@ -497,7 +497,7 @@ begin
     end;
 end;
 
-procedure TLine.GetBounds(out ABounds: TDoubleRect);
+procedure TLine.GetBounds(var ABounds: TDoubleRect);
 begin
   if not UseBounds then exit;
   case LineStyle of
@@ -1138,7 +1138,7 @@ begin
   end;
 end;
 
-procedure TFuncSeries.GetBounds(out ABounds: TDoubleRect);
+procedure TFuncSeries.GetBounds(var ABounds: TDoubleRect);
 begin
   with Extent do begin
     if UseXMin then ABounds.a.X := XMin;
@@ -1194,7 +1194,7 @@ begin
      FOnDraw(ACanvas, FChart.ClipRect);
 end;
 
-procedure TUserDrawnSeries.GetBounds(out ABounds: TDoubleRect);
+procedure TUserDrawnSeries.GetBounds(var ABounds: TDoubleRect);
 begin
   if Assigned(FOnGetBounds) then
     FOnGetBounds(ABounds);