diff --git a/src/blitter/8bpp_optimized.cpp b/src/blitter/8bpp_optimized.cpp
--- a/src/blitter/8bpp_optimized.cpp
+++ b/src/blitter/8bpp_optimized.cpp
@@ -112,7 +112,7 @@ void Blitter_8bppOptimized::Draw(Blitter
 	}
 }
 
-Sprite *Blitter_8bppOptimized::Encode(SpriteLoader::Sprite *sprite, AllocatorProc *allocator)
+Sprite *Blitter_8bppOptimized::Encode(const SpriteLoader::Sprite *sprite, AllocatorProc *allocator)
 {
 	/* Make memory for all zoom-levels */
 	uint memory = sizeof(SpriteData);