diff --git a/stones.lua b/stones.lua
index c97c1d5..268340a 100644
--- a/stones.lua
+++ b/stones.lua
@@ -47,6 +47,10 @@ local function reg(name, basename, basedef)
             type = "fixed",
             fixed = {-7/16, -8/16, -7/16, 7/16, 2/16, 7/16}
         },
+        collision_box = {
+            type = "fixed",
+            fixed = {-7/16, -8/16, -7/16, 7/16, 2/16, 7/16}
+        },
 
 
         tiles = {
@@ -91,7 +95,10 @@ local function reg(name, basename, basedef)
             type = "fixed",
             fixed = {-6/16, -8/16, -6/16, 6/16, 0/16, 6/16}
         },
-
+        collision_box = {
+            type = "fixed",
+            fixed = {-6/16, -8/16, -6/16, 6/16, 0/16, 6/16}
+        },
 
         tiles = {
             basedef.tiles[1]