diff --git a/src/blitter/32bpp_anim.hpp b/src/blitter/32bpp_anim.hpp
--- a/src/blitter/32bpp_anim.hpp
+++ b/src/blitter/32bpp_anim.hpp
@@ -29,6 +29,7 @@ public:
 	/* virtual */ void CopyFromBuffer(void *video, const void *src, int width, int height);
 	/* virtual */ void CopyToBuffer(const void *video, void *dst, int width, int height);
 	/* virtual */ void ScrollBuffer(void *video, int &left, int &top, int &width, int &height, int scroll_x, int scroll_y);
+	/* virtual */ int BufferSize(int width, int height);
 	/* virtual */ void PaletteAnimate(uint start, uint count);
 	/* virtual */ Blitter::PaletteAnimation UsePaletteAnimation();
 };