diff --git a/src/gfxinit.cpp b/src/gfxinit.cpp
--- a/src/gfxinit.cpp
+++ b/src/gfxinit.cpp
@@ -384,6 +384,8 @@ static void LoadSpriteTables()
 	assert(load_index == SPR_ONEWAY_BASE);
 	load_index += LoadGrfFile("oneway.grf", load_index, i++);
 
+	load_index++; // SPR_EMPTY_BOUNDING_BOX
+
 	assert(load_index == SPR_FLAGS_BASE);
 	load_index += LoadGrfFile("flags.grf", load_index, i++);