diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 9a719cf1d..c1f809ca1 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -3335,9 +3335,9 @@ static NSBitmapImageRep* rect_to_NSBitmapImageRep(Fl_Window *win, int x, int y,
 }
 
 unsigned char *Fl_X::bitmap_from_window_rect(Fl_Window *win, int x, int y, int w, int h, int *bytesPerPixel)
-/* Returns a capture of part of a mapped window as a pre-multiplied RGBA array of bytes.
- At present, alpha values are always 1 (or 0 for the angles of a window title bar)
- because only opaque colors are used to draw, so pre-multiplication can be ignored. 
+/* Returns a capture of a rectangle of a mapped window as a pre-multiplied RGBA array of bytes.
+ Alpha values are always 1 (except for the angles of a window title bar)
+ so pre-multiplication can be ignored. 
  *bytesPerPixel is always set to the value 4 upon return.
  delete[] the returned pointer after use
  */