diff --git a/lakefile b/lakefile
index 3e5b31f..44e01d5 100644
--- a/lakefile
+++ b/lakefile
@@ -19,7 +19,7 @@ target('build', try)
 
 install = target('install', {
   file.group{odir=LIBDIR;              src = try                              };
-  -- file.group{odir=LIBDIR;              src = J("src", "lua") ; recurse = true };
+  file.group{odir=LIBDIR;              src = J("src", "lua") ; recurse = true };
   -- file.group{odir=J(ROOT, 'examples'); src = 'examples';       recurse = true };
   file.group{odir=TESTDIR;             src = 'test';           recurse = true };
 })
diff --git a/rockspecs/try-scm-0.rockspec b/rockspecs/try-scm-0.rockspec
index 1694465..4632787 100644
--- a/rockspecs/try-scm-0.rockspec
+++ b/rockspecs/try-scm-0.rockspec
@@ -28,5 +28,6 @@ build = {
     try = {
       sources = { "src/try.c" },
     },
+    ["try.co"] =  "src/lua/try/co.lua",
   }
 }
diff --git a/src/lua/try/co.lua b/src/lua/try/co.lua
new file mode 100644
index 0000000..23cb92f
--- /dev/null
+++ b/src/lua/try/co.lua
@@ -0,0 +1,31 @@
+local try = require "try"
+
+local function _protect(co, status, ...)
+  if not status then
+    local msg = ...
+    if type(msg) == 'table' then
+      local k, v = next(msg)
+      if k == try.NIL then
+        if v == try.NIL then v = nil end
+        return nil, v
+      end
+    end
+    return error(msg, 0)
+  end
+  if coroutine.status(co) == "suspended" then
+    return _protect(co, coroutine.resume(co, coroutine.yield(...)))
+  else
+    return ...
+  end
+end
+
+local function protect(f)
+  return function(...)
+    local co = coroutine.create(f)
+    return _protect(co, coroutine.resume(co, ...))
+  end
+end
+
+return setmetatable({
+  protect = protect
+},{__index = try})
diff --git a/src/try.c b/src/try.c
index da412b9..c8072a9 100644
--- a/src/try.c
+++ b/src/try.c
@@ -14,7 +14,6 @@
 #  define EXPORT_API LUALIB_API
 #endif
 
-static const char *TRY_ERROR_IDX = "Dummy";
 static const char *TRY_ERROR_NIL = "NIL";
 
 /*=========================================================================*\
@@ -57,7 +56,7 @@ void lua_rawsetp (lua_State *L, int index, const void *p){
 \*-------------------------------------------------------------------------*/
 static int try_check_error(lua_State *L) {
   if(lua_istable(L, -1)){
-    lua_rawgetp(L, -1, TRY_ERROR_IDX);
+    lua_rawgetp(L, -1, TRY_ERROR_NIL);
 
     if(lua_isnil(L, -1)){ /*not try error*/
       lua_pop(L, 1);
@@ -85,7 +84,7 @@ static int try_error(lua_State *L){
   else{
     lua_pushvalue(L, -2);
   }
-  lua_rawsetp(L, -2, TRY_ERROR_IDX);
+  lua_rawsetp(L, -2, TRY_ERROR_NIL);
   return lua_error(L);
 }
 
@@ -198,5 +197,8 @@ EXPORT_API int luaopen_try(lua_State *L) {
   lua_pushcclosure(L, try_assert, 1);
   lua_setfield(L, -2, "assert");
 
+  lua_pushlightuserdata(L, (void*)TRY_ERROR_NIL);
+  lua_setfield(L, -2, "NIL");
+
   return 1;
 }
diff --git a/test/test.lua b/test/test.lua
index bc97c07..1020cf5 100644
--- a/test/test.lua
+++ b/test/test.lua
@@ -134,7 +134,11 @@ end)
 
 end
 
-local _ENV = TEST_CASE'try.coro' if ENABLE and not IS_LUA_51 then
+local _ENV = TEST_CASE'try.coro' if ENABLE then
+
+local try = try
+
+if IS_LUA_51 then try = require "try.co" end
 
 local it = setmetatable(_ENV or _M, {__call = function(self, describe, fn)
   self["test " .. describe] = fn