diff --git a/lualib-src/sproto/lsproto.c b/lualib-src/sproto/lsproto.c
index cb332027..16d36554 100644
--- a/lualib-src/sproto/lsproto.c
+++ b/lualib-src/sproto/lsproto.c
@@ -55,6 +55,13 @@ static int64_t lua_tointegerx(lua_State *L, int idx, int *isnum) {
 		return 0;
 	}
 }
+
+static int lua_absindex (lua_State *L, int idx) {
+	if (idx > 0 || idx <= LUA_REGISTRYINDEX)
+		return idx;
+	return lua_gettop(L) + idx + 1;
+}
+
 #endif
 
 static void
@@ -235,6 +242,11 @@ encode(const struct sproto_arg *args) {
 			return 8;
 		}
 	}
+	case SPROTO_DOUBLE: {
+		lua_Number v = lua_tonumber(L, -1);
+		*(double*)args->value = (double)v;
+		return 8;
+	}
 	case SPROTO_TBOOLEAN: {
 		int v = lua_toboolean(L, -1);
 		if (!lua_isboolean(L,-1)) {
@@ -395,6 +407,11 @@ decode(const struct sproto_arg *args) {
 		}
 		break;
 	}
+	case SPROTO_DOUBLE: {
+		double v = *(double*)args->value;
+		lua_pushnumber(L, v);
+		break;
+	}
 	case SPROTO_TBOOLEAN: {
 		int v = *(uint64_t*)args->value;
 		lua_pushboolean(L,v);
@@ -671,6 +688,9 @@ push_default(const struct sproto_arg *args, int array) {
 		else
 			lua_pushinteger(L, 0);
 		break;
+	case SPROTO_DOUBLE:
+		lua_pushnumber(L, 0.0);
+		break;
 	case SPROTO_TBOOLEAN:
 		lua_pushboolean(L, 0);
 		break;
diff --git a/lualib-src/sproto/sproto.c b/lualib-src/sproto/sproto.c
index 2c36ad9f..4d38d51c 100644
--- a/lualib-src/sproto/sproto.c
+++ b/lualib-src/sproto/sproto.c
@@ -944,6 +944,7 @@ sproto_encode(const struct sproto_type *st, void * buffer, int size, sproto_call
 			args.type = type;
 			args.index = 0;
 			switch(type) {
+			case SPROTO_DOUBLE:
 			case SPROTO_TINTEGER:
 			case SPROTO_TBOOLEAN: {
 				union {
@@ -1177,6 +1178,7 @@ sproto_decode(const struct sproto_type *st, const void * data, int size, sproto_
 				}
 			} else {
 				switch (f->type) {
+				case SPROTO_DOUBLE:
 				case SPROTO_TINTEGER: {
 					uint32_t sz = todword(currentdata);
 					if (sz == SIZEOF_INT32) {
diff --git a/lualib-src/sproto/sproto.h b/lualib-src/sproto/sproto.h
index f70309ec..1fb9252e 100644
--- a/lualib-src/sproto/sproto.h
+++ b/lualib-src/sproto/sproto.h
@@ -13,7 +13,8 @@ struct sproto_type;
 #define SPROTO_TINTEGER 0
 #define SPROTO_TBOOLEAN 1
 #define SPROTO_TSTRING 2
-#define SPROTO_TSTRUCT 3
+#define SPROTO_DOUBLE 3
+#define SPROTO_TSTRUCT 4
 
 // sub type of string (sproto_arg.extra)
 #define SPROTO_TSTRING_STRING 0
diff --git a/lualib/sprotoparser.lua b/lualib/sprotoparser.lua
index 4c9a7d07..afac92f7 100644
--- a/lualib/sprotoparser.lua
+++ b/lualib/sprotoparser.lua
@@ -97,7 +97,10 @@ local convert = {}
 function convert.protocol(all, obj)
 	local result = { tag = obj[2] }
 	for _, p in ipairs(obj[3]) do
-		assert(result[p[1]] == nil)
+		local pt = p[1]
+		if result[pt] ~= nil then
+			error(string.format("redefine %s in protocol %s", pt, obj[1]))
+		end
 		local typename = p[2]
 		if type(typename) == "table" then
 			local struct = typename
@@ -179,6 +182,7 @@ local buildin_types = {
 	boolean = 1,
 	string = 2,
 	binary = 2,	-- binary is a sub type of string
+	double = 3,
 }
 
 local function checktype(types, ptype, t)