Problem with BufferedBitmap (API level 4.0.x)

When trying to compile my code for Fenix 7 devices (target API level 4.0.x) I'm getting the following error:

Error: Symbol Not Found Error
Details: Failed invoking <symbol>
Stack:
- onLayout() at G:\CIQ\TactixFace\source\TactixFaceView.mc:91 0x10000185

It is related to the part of the code, where an offscreen buffer is defined (see below). I can't see any error in the code, it works fine with all previous devices and API levels, and it is also consistent with the current API documentation. Has anybody else experienced similar issues with the new CIQ SDK (4.0.7)? How can be this resolved? I'll be grateful for any feedback.

The code:

using Toybox.Graphics as Gfx;

var offscreenBuffer;

var buffer_size;

// offscreenBuffer size
buffer_size = dc.getWidth();

// allocate the buffer for drawing
if( Gfx has :BufferedBitmap ) {
  offscreenBuffer = new Gfx.BufferedBitmap({
   :width=>buffer_size,
   :height=>buffer_size,
   :palette=>[]
  });

} else {
  offscreenBuffer = null;
}