diff --git a/src/lib_debug.c b/src/lib_debug.c
index d90c422f..0330f1d2 100644
--- a/src/lib_debug.c
+++ b/src/lib_debug.c
@@ -224,6 +224,37 @@ LJLIB_CF(debug_setupvalue)
   return debug_getupvalue(L, 0);
 }
 
+LJLIB_CF(debug_upvalueid)
+{
+  GCfunc *fn = lj_lib_checkfunc(L, 1);
+  int32_t n = lj_lib_checkint(L, 2) - 1;
+  if ((uint32_t)n >= fn->l.nupvalues)
+    lj_err_arg(L, 2, LJ_ERR_IDXRNG);
+  setlightudV(L->top-1, isluafunc(fn) ? (void *)gcref(fn->l.uvptr[n]) :
+					(void *)&fn->c.upvalue[n]);
+  return 1;
+}
+
+LJLIB_CF(debug_upvaluejoin)
+{
+  GCfunc *fn[2];
+  GCRef *p[2];
+  int i;
+  for (i = 0; i < 2; i++) {
+    int32_t n;
+    fn[i] = lj_lib_checkfunc(L, 2*i+1);
+    if (!isluafunc(fn[i]))
+      lj_err_arg(L, 2*i+1, LJ_ERR_NOLFUNC);
+    n = lj_lib_checkint(L, 2*i+2) - 1;
+    if ((uint32_t)n >= fn[i]->l.nupvalues)
+      lj_err_arg(L, 2*i+2, LJ_ERR_IDXRNG);
+    p[i] = &fn[i]->l.uvptr[n];
+  }
+  setgcrefr(*p[0], *p[1]);
+  lj_gc_objbarrier(L, fn[0], gcref(*p[1]));
+  return 0;
+}
+
 /* ------------------------------------------------------------------------ */
 
 static const char KEY_HOOK = 'h';
diff --git a/src/lj_api.c b/src/lj_api.c
index bfd471d2..a9ea38d8 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -852,6 +852,26 @@ LUA_API const char *lua_getupvalue(lua_State *L, int idx, int n)
   return name;
 }
 
+LUA_API void *lua_upvalueid(lua_State *L, int idx, int n)
+{
+  GCfunc *fn = funcV(index2adr(L, idx));
+  n--;
+  api_check(L, (uint32_t)n < fn->l.nupvalues);
+  return isluafunc(fn) ? (void *)gcref(fn->l.uvptr[n]) :
+			 (void *)&fn->c.upvalue[n];
+}
+
+LUA_API void lua_upvaluejoin(lua_State *L, int idx1, int n1, int idx2, int n2)
+{
+  GCfunc *fn1 = funcV(index2adr(L, idx1));
+  GCfunc *fn2 = funcV(index2adr(L, idx2));
+  n1--; n2--;
+  api_check(L, isluafunc(fn1) && (uint32_t)n1 < fn1->l.nupvalues);
+  api_check(L, isluafunc(fn2) && (uint32_t)n2 < fn2->l.nupvalues);
+  setgcrefr(fn1->l.uvptr[n1], fn2->l.uvptr[n2]);
+  lj_gc_objbarrier(L, fn1, gcref(fn1->l.uvptr[n1]));
+}
+
 LUALIB_API void *luaL_checkudata(lua_State *L, int idx, const char *tname)
 {
   cTValue *o = index2adr(L, idx);
diff --git a/src/lj_errmsg.h b/src/lj_errmsg.h
index c07d4387..28c5ca08 100644
--- a/src/lj_errmsg.h
+++ b/src/lj_errmsg.h
@@ -44,6 +44,7 @@ ERRDEF(BADVAL,	"invalid value")
 ERRDEF(NOVAL,	"value expected")
 ERRDEF(NOCORO,	"coroutine expected")
 ERRDEF(NOTABN,	"nil or table expected")
+ERRDEF(NOLFUNC,	"Lua function expected")
 ERRDEF(NOFUNCL,	"function or level expected")
 ERRDEF(NOSFT,	"string/function/table expected")
 ERRDEF(NOPROXY,	"boolean or proxy expected")
diff --git a/src/lua.h b/src/lua.h
index 0e98b374..9e9357a8 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -336,12 +336,15 @@ LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);
 LUA_API const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);
 LUA_API const char *lua_getupvalue (lua_State *L, int funcindex, int n);
 LUA_API const char *lua_setupvalue (lua_State *L, int funcindex, int n);
-
 LUA_API int lua_sethook (lua_State *L, lua_Hook func, int mask, int count);
 LUA_API lua_Hook lua_gethook (lua_State *L);
 LUA_API int lua_gethookmask (lua_State *L);
 LUA_API int lua_gethookcount (lua_State *L);
 
+/* From Lua 5.2. */
+LUA_API void *lua_upvalueid (lua_State *L, int idx, int n);
+LUA_API void lua_upvaluejoin (lua_State *L, int idx1, int n1, int idx2, int n2);
+
 
 struct lua_Debug {
   int event;