diff --git a/src/main.lua b/src/main.lua
index 3a82cf9..d7cd04c 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -75,7 +75,7 @@ local function load(name)
     return content["buf"],content["dimensions"]
 end
 local function bufistype(buf, x,y,z, targettype)
-    return buf[posasstring(x,y,z)] == targettype or (targettype == 0 and not buf[posasstring(x,y,z)])
+    return buf[posasstring(x,y,z)] == targettype or (targettype == 0 and buf[posasstring(x,y,z)] == nil)
 end
 local function fill_getneighbors(x,y,z, sx,sz, seltype,buf)
     local out = {}