diff --git a/src/drawing/drawing.c b/src/drawing/drawing.c
index cb75ded2b0..00d5ef84c4 100644
--- a/src/drawing/drawing.c
+++ b/src/drawing/drawing.c
@@ -211,7 +211,7 @@ uint8* gfx_get_dirty_blocks()
  * right (dx)
  * bottom (bp)
  */
-void gfx_set_dirty_blocks(uint16 left, uint16 top, uint16 right, uint16 bottom)
+void gfx_set_dirty_blocks(sint16 left, sint16 top, sint16 right, sint16 bottom)
 {
 	int x, y;
 	uint8 *screenDirtyBlocks = gfx_get_dirty_blocks();
diff --git a/src/drawing/drawing.h b/src/drawing/drawing.h
index a6269c8f01..97ec0b81e1 100644
--- a/src/drawing/drawing.h
+++ b/src/drawing/drawing.h
@@ -80,7 +80,7 @@ extern rct_gx g2;
 
 // 
 rct_drawpixelinfo* clip_drawpixelinfo(rct_drawpixelinfo* dpi, int left, int width, int top, int height);
-void gfx_set_dirty_blocks(uint16 left, uint16 top, uint16 right, uint16 bottom);
+void gfx_set_dirty_blocks(sint16 left, sint16 top, sint16 right, sint16 bottom);
 void gfx_draw_all_dirty_blocks();
 void gfx_redraw_screen_rect(short left, short top, short right, short bottom);
 void gfx_invalidate_screen();