diff --git a/compatibility.lua b/compatibility.lua
index 8ca18b5..fcf4660 100644
--- a/compatibility.lua
+++ b/compatibility.lua
@@ -1,3 +1,21 @@
+local function version_is_lower(v1, v2)
+	local d1, c1, d2, c2
+	while #v1 > 0 and #v2 > 0 do
+		d1, c1, v1 = v1:match("^(%d*)(%D*)(.*)$")
+		d2, c2, v2 = v2:match("^(%d*)(%D*)(.*)$")
+
+		d1 = tonumber(d1) or -1
+		d2 = tonumber(d2) or -1
+		if d1 ~= d2 then
+			return d1 < d2
+		end
+		if c1 ~= c2 then
+			return c1 < c2
+		end
+	end
+	return false
+end
+
 local function fix_min_catchment(settings, is_global)
 	local prefix = is_global and "mapgen_rivers_" or ""
 
@@ -21,6 +39,18 @@ local function fix_compatibility_minetest(settings)
 	if previous_version == "0.0" then
 		fix_min_catchment(settings, true)
 	end
+
+	if version_is_lower(previous_version, "1.0.2-dev1") then
+		local blocksize = tonumber(settings:get("mapgen_rivers_blocksize") or 15)
+		local grid_x_size = tonumber(settings:get("mapgen_rivers_grid_x_size"))
+		if grid_x_size then
+			settings:set("mapgen_rivers_map_x_size", tostring(grid_x_size * blocksize))
+		end
+		local grid_z_size = tonumber(settings:get("mapgen_rivers_grid_z_size"))
+		if grid_z_size then
+			settings:set("mapgen_rivers_map_z_size", tostring(grid_z_size * blocksize))
+		end
+	end
 end
 
 local function fix_compatibility_mapgen_rivers(settings)
@@ -29,6 +59,18 @@ local function fix_compatibility_mapgen_rivers(settings)
 	if previous_version == "0.0" then
 		fix_min_catchment(settings, false)
 	end
+
+	if version_is_lower(previous_version, "1.0.2-dev1") then
+		local blocksize = tonumber(settings:get("blocksize") or 15)
+		local grid_x_size = tonumber(settings:get("grid_x_size"))
+		if grid_x_size then
+			settings:set("map_x_size", tostring(grid_x_size * blocksize))
+		end
+		local grid_z_size = tonumber(settings:get("grid_z_size"))
+		if grid_z_size then
+			settings:set("map_z_size", tostring(grid_z_size * blocksize))
+		end
+	end
 end
 
 return fix_compatibility_minetest, fix_compatibility_mapgen_rivers
diff --git a/polygons.lua b/polygons.lua
index c531b2b..d905663 100644
--- a/polygons.lua
+++ b/polygons.lua
@@ -11,8 +11,9 @@ dofile(modpath .. 'load.lua')
 
 mapgen_rivers.grid = {}
 
-local X = mapgen_rivers.settings.grid_x_size
-local Z = mapgen_rivers.settings.grid_z_size
+local blocksize = mapgen_rivers.settings.blocksize
+local X = math.floor(mapgen_rivers.settings.map_x_size / blocksize)
+local Z = math.floor(mapgen_rivers.settings.map_z_size / blocksize)
 
 local function offset_converter(o)
 	return (o + 0.5) * (1/256)
@@ -80,7 +81,6 @@ local function index(x, z)
 	return z*X+x+1
 end
 
-local blocksize = mapgen_rivers.settings.blocksize
 local min_catchment = mapgen_rivers.settings.min_catchment
 local max_catchment = mapgen_rivers.settings.max_catchment
 
diff --git a/pregenerate.lua b/pregenerate.lua
index 7e97e48..0797dc1 100644
--- a/pregenerate.lua
+++ b/pregenerate.lua
@@ -18,6 +18,10 @@ local function pregenerate(keep_loaded)
 	local grid = mapgen_rivers.grid
 	local size = grid.size
 
+	if size.x * size.y > 4e6 then
+		minetest.log("warning", "[mapgen_rivers] You are going to generate a very large grid (>4M nodes). If you experience problems, you should increase blocksize or reduce map size.")
+	end
+
 	local seed = tonumber(minetest.get_mapgen_setting("seed"))
 	np_base.seed = (np_base.seed or 0) + seed
 
diff --git a/settings.lua b/settings.lua
index 2d64a40..a7aee00 100644
--- a/settings.lua
+++ b/settings.lua
@@ -1,7 +1,7 @@
 local mtsettings = minetest.settings
 local mgrsettings = Settings(minetest.get_worldpath() .. '/mapgen_rivers.conf')
 
-mapgen_rivers.version = "1.0.2"
+mapgen_rivers.version = "1.0.2-dev1"
 
 local previous_version_mt = mtsettings:get("mapgen_rivers_version") or "0.0"
 local previous_version_mgr = mgrsettings:get("version") or "0.0"
@@ -93,8 +93,8 @@ mapgen_rivers.settings = {
 	glacier_factor = def_setting('glacier_factor', 'number'),
 	elevation_chill = def_setting('elevation_chill', 'number'),
 
-	grid_x_size = def_setting('grid_x_size', 'number'),
-	grid_z_size = def_setting('grid_z_size', 'number'),
+	map_x_size = def_setting('map_x_size', 'number'),
+	map_z_size = def_setting('map_z_size', 'number'),
 	evol_params = {
 		K = def_setting('river_erosion_coef', 'number'),
 		m = def_setting('river_erosion_power', 'number'),
diff --git a/settings_default.json b/settings_default.json
index 15d32d1..0105832 100644
--- a/settings_default.json
+++ b/settings_default.json
@@ -13,8 +13,8 @@
 	"glacier_factor": 8,
 	"elevation_chill": 0.25,
 
-	"grid_x_size": 1000,
-	"grid_z_size": 1000,
+	"map_x_size": 15000,
+	"map_z_size": 15000,
 	"river_erosion_coef": 0.5,
 	"river_erosion_power": 0.4,
 	"diffusive_erosion": 0.5,
diff --git a/settingtypes.txt b/settingtypes.txt
index 455a6b0..6446541 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -3,19 +3,25 @@
 #    Whether the map should be centered at x=0, z=0.
 mapgen_rivers_center (Center map) bool true
 
-#    Represents horizontal map scale. Every cell of the grid will be upscaled to
-#    a square of this size.
-#    For example if the grid size is 1000x1000 and block size is 12,
-#    the actual size of the map will be 12000.
+#    Every cell of the river grid will represent a square of this size.
+#    A lower value will result in more detailed terrain and finer computation
+#    of rivers, but will be slower to generate and use more resources.
+#
+#    WARNING: Excessively low values may cause crashes at pre-generation, due to
+#    memory issues
 mapgen_rivers_blocksize (Block size) float 15.0 2.0 100.0
 
-#    X size of the grid being generated
-#    Actual size of the map is grid_x_size * blocksize
-mapgen_rivers_grid_x_size (Grid X size) int 1000 50 5000
+#    X size of the map being generated
+#
+#    X size of the river grid will be this/blocksize
+#    When increasing, it is recommended to increase blocksize too
+mapgen_rivers_map_x_size (Map X size) int 15000 500 66000
 
-#    Z size of the grid being generated
-#    Actual size of the map is grid_z_size * blocksize
-mapgen_rivers_grid_z_size (Grid Z size) int 1000 50 5000
+#    Z size of the map being generated
+#
+#    Z size of the river grid will be this/blocksize
+#    When increasing, it is recommended to increase blocksize too
+mapgen_rivers_map_z_size (Map Z size) int 15000 500 66000
 
 #    Minimal catchment area for a river to be drawn, in square nodes
 #    Lower value means bigger river density