diff --git a/src/main.lua b/src/main.lua
index c77929d..4e68732 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -54,16 +54,16 @@ local function load_map(map_file_name)
   minimums = {math.huge, math.huge}   -- x, z
   maximums = {-math.huge, -math.huge} -- x, z
   for _, node in pairs(nodes) do
-    if node[1] > maximums[1] then
+    if node[1] > maximums[1] and node[4] ~= false then
       maximums[1] = node[1]
     end
-    if node[1] < minimums[1] then
+    if node[1] < minimums[1] and node[4] ~= false then
       minimums[1] = node[1]
     end
-    if node[3] > maximums[2] then
+    if node[3] > maximums[2] and node[4] ~= false then
       maximums[2] = node[3]
     end
-    if node[3] < minimums[2] then
+    if node[3] < minimums[2] and node[4] ~= false then
       minimums[2] = node[3]
     end
   end