diff --git a/worldedit/serialization.lua b/worldedit/serialization.lua
index 58c0001..57749fc 100644
--- a/worldedit/serialization.lua
+++ b/worldedit/serialization.lua
@@ -85,27 +85,27 @@ function worldedit.serialize(pos1, pos2)
 		array[1] = first_value
 		return {first_value}
 	end
-	local function match_try(cache, value)
+	local function match_try(array, cache, value)
 		local i = #cache
 		while i >= 1 do
 			if cache[i] == value then
-				return -(#cache - i + 1)
+				local ret = -(#cache - i + 1)
+				return ret, array[#array] == ret
 			end
 			i = i - 1
 		end
-		return nil
+		return nil, false
 	end
 	local function match_push(array, cache, match, value)
-		if match ~= nil then -- don't advance cache
-			array[#array + 1] = match
-			return
+		if match ~= nil then -- don't advance ringbuffer
+			return match
 		end
 		local idx = #cache + 1
 		cache[idx] = value
 		if idx > MATCH_DIST then
 			table.remove(cache, 1)
 		end
-		array[#array + 1] = value
+		return value
 	end
 	-- Helper functions (2)
 	local function cur_new(pos, pos1)
@@ -119,15 +119,33 @@ function worldedit.serialize(pos1, pos2)
 		}
 	end
 	local function cur_finish(result, cur)
-		if #cur.param1 == 1 and cur.param1[1] == 0 then
+		-- TODO: wouldn't be needed if param1, param2 supported omit (see below)
+		local i = #cur.param1
+		while i > 1 and cur.param1[i] == -1 do
+			cur.param1[i] = nil
+			i = i - 1
+		end
+		if i == 1 and cur.param1[1] == 0 then
 			cur.param1 = nil
 		end
-		if #cur.param2 == 1 and cur.param2[1] == 0 then
+
+		i = #cur.param2
+		while i > 1 and cur.param2[i] == -1 do
+			cur.param2[i] = nil
+			i = i - 1
+		end
+		if i == 1 and cur.param2[1] == 0 then
 			cur.param2 = nil
 		end
+		-- Drop unneeded ref from data table (FIXME?)
+		i = #cur.data
+		if cur.data[i] == -1 then
+			cur.data[i] = nil
+		end
+		-- add to result table
 		result[#result + 1] = cur
 	end
-	--magic number: 24
+	local OMIT_MIN_LIMIT = 18
 
 	-- Serialize stuff
 	local pos = {}
@@ -135,6 +153,7 @@ function worldedit.serialize(pos1, pos2)
 	local result = {}
 	local cur
 	local cache_data, cache_param1, cache_param2
+	local is_omit -- applies to data only
 	pos[other1] = pos1[other1]
 	while pos[other1] <= pos2[other1] do
 		pos[other2] = pos1[other2]
@@ -144,26 +163,65 @@ function worldedit.serialize(pos1, pos2)
 
 				local node = get_node(pos)
 				if node.name ~= "air" and node.name ~= "ignore" then
-					if cur == nil then -- Start a new row
+					local new_row = false
+					if cur == nil then
+						new_row = true
+					else -- See if we want to push to existing row
+						local next_c = cur.c + 1
+						cur.c = next_c
+						local value, m, can_omit
+
+						value = node.name
+						m, can_omit = match_try(cur.data, cache_data, node.name)
+						if is_omit and not can_omit then
+							-- we have omitted previous entries, but can't omit this one
+							if next_c - #cur.data > OMIT_MIN_LIMIT then
+								-- just starting a new row will take less space, do that
+								new_row = true
+							else
+								-- fill up omitted data and proceed as usual
+								local last = cur.data[#cur.data]
+								for i = #cur.data + 1, next_c - 1 do
+									cur.data[i] = last
+								end
+								cur.data[next_c] = match_push(cur.data, cache_data, m, value)
+								is_omit = false
+							end
+						elseif can_omit then
+							is_omit = true
+						else
+							cur.data[next_c] = match_push(cur.data, cache_data, m, value)
+						end
+
+						-- TODO: implement omit for param1, param2 too
+						if not new_row then
+							value = node.param1
+							m, can_omit = match_try(cur.param1, cache_param1, value)
+							cur.param1[next_c] = match_push(cur.param1, cache_param1, m, value)
+
+							value = node.param2
+							m, can_omit = match_try(cur.param2, cache_param2, value)
+							cur.param2[next_c] = match_push(cur.param2, cache_param2, m, value)
+						else -- Undo changes and finish row
+							cur.c = next_c - 1
+							cur_finish(result, cur)
+							cur = nil
+							is_omit = false
+						end
+					end
+
+					if new_row then -- Start a new row
 						cur = cur_new(pos, pos1, axis, other1, other2)
 						cache_data = match_init(cur.data, node.name)
 						cache_param1 = match_init(cur.param1, node.param1)
 						cache_param2 = match_init(cur.param2, node.param2)
-					else -- Push to existing row
-						local next_c = cur.c + 1
-						cur.c = next_c
-						local v = node.name
-						match_push(cur.data, cache_data, match_try(cache_data, v), v)
-						v = node.param1
-						match_push(cur.param1, cache_param1, match_try(cache_param1, v), v)
-						v = node.param2
-						match_push(cur.param2, cache_param2, match_try(cache_param2, v), v)
 					end
 					count = count + 1
 				else
 					if cur ~= nil then -- Finish row
 						cur_finish(result, cur)
 						cur = nil
+						is_omit = false
 					end
 				end
 				pos[axis] = pos[axis] + 1
@@ -172,11 +230,13 @@ function worldedit.serialize(pos1, pos2)
 			if cur ~= nil then -- Finish leftover row
 				cur_finish(result, cur)
 				cur = nil
+				is_omit = false
 			end
 			pos[other2] = pos[other2] + 1
 		end
 		pos[other1] = pos[other1] + 1
 	end
+
 	-- Serialize entries
 	result = minetest.serialize(result)
 	return tonumber(worldedit.LATEST_SERIALIZATION_VERSION) .. "," ..