diff --git a/mods/CORE/mcl_init/init.lua b/mods/CORE/mcl_init/init.lua
index 9568fa0ce5..c68df274f0 100644
--- a/mods/CORE/mcl_init/init.lua
+++ b/mods/CORE/mcl_init/init.lua
@@ -57,10 +57,16 @@ mcl_vars.mg_overworld_max = 31000
 mcl_vars.mg_nether_min = -29067 -- Carefully chosen to be at a mapchunk border
 mcl_vars.mg_nether_max = mcl_vars.mg_nether_min + 128
 mcl_vars.mg_bedrock_nether_bottom_min = mcl_vars.mg_nether_min
-mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min + 4
 mcl_vars.mg_bedrock_nether_top_max = mcl_vars.mg_nether_max
-mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max - 4
 mcl_vars.mg_lava_nether_max = mcl_vars.mg_nether_min + 31
+if mg_name ~= "flat" then
+	mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min + 4
+	mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max - 4
+else
+	-- Thin bedrock in flat mapgen
+	mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min
+	mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max
+end
 
 -- The End (surface at ca. Y = -27000)
 mcl_vars.mg_end_min = -27073 -- Carefully chosen to be at a mapchunk border