diff --git a/lcl/interfaces/gtk3/gtk3winapih.inc b/lcl/interfaces/gtk3/gtk3winapih.inc
index 57e2ee2d5c..5f25e0d088 100644
--- a/lcl/interfaces/gtk3/gtk3winapih.inc
+++ b/lcl/interfaces/gtk3/gtk3winapih.inc
@@ -117,7 +117,6 @@ function GetCurrentObject(DC: HDC; uObjectType: UINT): HGDIOBJ; override;
 function GetCursorPos(var lpPoint: TPoint): Boolean; override;
 function GetDC(hWnd: HWND): HDC;  override;
 function GetDCOriginRelativeToWindow(PaintDC: HDC; WindowHandle: HWND; var OriginDiff: TPoint): boolean; override;
-function GetDesignerDC(WindowHandle: HWND): HDC; override;
 function GetDeviceCaps(DC: HDC; Index: Integer): Integer; override;
 function GetDeviceSize(DC: HDC; var p: TPoint): boolean; override;
 function GetDIBits(DC: HDC; Bitmap: HBitmap; StartScan, NumScans: UINT; Bits: Pointer; var BitInfo: BitmapInfo; Usage: UINT): Integer; override;