diff --git a/lcl/checklst.pas b/lcl/checklst.pas
index b6031c2632..3d731f5d00 100644
--- a/lcl/checklst.pas
+++ b/lcl/checklst.pas
@@ -70,7 +70,7 @@ type
     constructor Create(AOwner: TComponent); override;
     procedure MeasureItem(Index: Integer; var TheHeight: Integer); override;
     procedure Toggle(AIndex: Integer);
-    procedure CheckAll(AState: TCheckBoxState; AllowGrayed: Boolean = True; AllowDisabled: Boolean = True);
+    procedure CheckAll(AState: TCheckBoxState; aAllowGrayed: Boolean = True; aAllowDisabled: Boolean = True);
     
     property AllowGrayed: Boolean read FAllowGrayed write FAllowGrayed default False;
     property Checked[AIndex: Integer]: Boolean read GetChecked write SetChecked;
@@ -216,12 +216,12 @@ begin
 end;
 
 procedure TCustomCheckListBox.CheckAll(AState: TCheckBoxState;
-  AllowGrayed: Boolean; AllowDisabled: Boolean);
+  aAllowGrayed: Boolean; aAllowDisabled: Boolean);
 var
   i: Integer;
 begin
   for i := 0 to Items.Count - 1 do begin
-    if (AllowGrayed or (State[i] <> cbGrayed)) and (AllowDisabled or ItemEnabled[i]) then
+    if (aAllowGrayed or (State[i] <> cbGrayed)) and (aAllowDisabled or ItemEnabled[i]) then
       State[i] := AState;
   end;
 end;