diff --git a/lua_cmsgpack.c b/lua_cmsgpack.c
index 786daab..fbe8d6a 100644
--- a/lua_cmsgpack.c
+++ b/lua_cmsgpack.c
@@ -40,7 +40,7 @@
 #if BITS_32
     #define lua_pushunsigned(L, n) lua_pushnumber(L, n)
 #else
-    #define lua_pushunsigned(L, n) lua_pushinteger(L, n)
+    #define lua_pushunsigned(L, n) ((sizeof(lua_Integer) == 4) ? lua_pushnumber(L, n) : lua_pushinteger(L, n))
 #endif
 
 /* =============================================================================
@@ -517,8 +517,10 @@ static int mp_pack(lua_State *L) {
     int i;
     mp_buf *buf;
 
-    if (nargs == 0)
-        return luaL_argerror(L, 0, "MessagePack pack needs input.");
+    if (nargs == 0){
+        lua_pushliteral(L, "");
+        return 1;
+    }
 
     buf = mp_buf_new(L);
     for(i = 1; i <= nargs; i++) {
diff --git a/test.lua b/test.lua
index f7eed34..4860e32 100644
--- a/test.lua
+++ b/test.lua
@@ -122,6 +122,10 @@ function test_circular(name,obj)
     end
 end
 
+local function npack(...)
+    return select("#", ...), {...}
+end
+
 function test_stream(mod, name, ...)
     io.write("Stream test '", name, "' ...\n")
     if not mod then
@@ -133,27 +137,31 @@ function test_stream(mod, name, ...)
     for i=1, argc do
         test_circular(name, select(i, ...))
     end
-    local ret = {mod.unpack(mod.pack(unpack({...})))}
+    local n, ret = npack(mod.unpack(mod.pack(unpack({...}))))
+    if n ~= argc then
+        print("  ERRORn:", "number of result not match ", n, argc)
+        failed = failed + 1
+    end
     for i=1, argc do
         local origin = select(i, ...)
         if (type(origin) == "table") then
             for k,v in pairs(origin) do
                 local fail = not compare_objects(v, ret[i][k])
                 if fail then
-                    print("ERRORa:", k, v, " not match ", ret[i][k])
+                    print("  ERRORa:", k, v, " not match ", ret[i][k])
                     failed = failed + 1
                 elseif not fail then
-                    print("ok; matched stream table member")
+                    print("  ok; matched stream table member")
                     passed = passed + 1
                 end
             end
         else
             local fail = not compare_objects(origin, ret[i])
             if fail then
-                print("ERRORc:", origin, " not match ", ret[i])
+                print("  ERRORc:", origin, " not match ", ret[i])
                 failed = failed + 1
             elseif not fail then
-                print("ok; matched individual stream member")
+                print("  ok; matched individual stream member")
                 passed = passed + 1
             end
         end
@@ -326,6 +334,7 @@ end
 
 test_global()
 test_array()
+test_circular("nothing");
 test_circular("positive fixnum",17);
 test_circular("negative fixnum",-1);
 test_circular("true boolean",true);
@@ -418,8 +427,11 @@ test_stream(cmsgpack, "oddities", {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0}, {a=64}
 test_stream(cmsgpack_safe, "safe oddities", {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0}, {a=64}, math.huge, -math.huge)
 test_stream(cmsgpack, "strange things", nil, {}, {nil}, a, b, b, b, a, a, b, {c = a, d = b})
 test_stream(cmsgpack_safe, "strange things", nil, {}, {nil}, a, b, b, b, a, a, b, {c = a, d = b})
-test_error("pack nothing", function() cmsgpack.pack() end)
+test_noerror("pack nothing", function() cmsgpack.pack() end)
 test_noerror("pack nothing safe", function() cmsgpack_safe.pack() end)
+test_stream(cmsgpack, "pack nothing")
+test_stream(cmsgpack_safe, "pack nothing")
+
 test_circular("large object test",
     {A=9483, a=9483, aa=9483, aal=9483, aalii=9483, aam=9483, Aani=9483,
     aardvark=9483, aardwolf=9483, Aaron=9483, Aaronic=9483, Aaronical=9483,