diff --git a/init.lua b/init.lua
index 2fd99a6..40fc4e3 100644
--- a/init.lua
+++ b/init.lua
@@ -88,7 +88,7 @@ if setting ~= nil then
 end
 
 -- Max. and min. heights between rail corridors are generated
-local height_min = -31000
+local height_min = -30900
 local height_max = -30
 setting = tonumber(minetest.settings:get("tsm_railcorridors_height_min"))
 if setting then
@@ -827,7 +827,7 @@ local function start_corridor(waypoint, coord, sign, length, wood, post, damage,
 				up = true
 			else
 				-- Chose random direction in between
-				up = pr:next(0, 2) < 1
+				up = pr:next(1, 2) == 1
 			end
 		else
 			ud = false
diff --git a/settingtypes.txt b/settingtypes.txt
index 8cd03b0..5f03003 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -35,10 +35,10 @@ tsm_railcorridors_place_cobwebs (Cobwebs) bool true
 tsm_railcorridors_probability_damage (Damaged railway probability) float 0.55 0.0 1.0
 
 #Minimum height in which rail corridors are created.
-tsm_railcorridors_height_min (Minimum height) int -31000 -31000 31000
+tsm_railcorridors_height_min (Minimum height) int -30900
 
 #Maximum height in which rail corridors are created.
-tsm_railcorridors_height_max (Maximum height) int -30 -31000 31000
+tsm_railcorridors_height_max (Maximum height) int -30
 
 #If enabled, rail corridors continue to generate through obstacles such
 #as other rail corridors (without destroying them, mostly). This may lead