diff --git a/luprex/ext/eris-master/src/ldo.c b/luprex/ext/eris-master/src/ldo.c
index f85a1856..7cd523a4 100644
--- a/luprex/ext/eris-master/src/ldo.c
+++ b/luprex/ext/eris-master/src/ldo.c
@@ -102,6 +102,9 @@ static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
   L->top = oldtop + 1;
 }
 
+LUA_API int lua_isthrowing (lua_State *L) {
+  return ((L->errorJmp != NULL) && (L->errorJmp->status != LUA_OK));
+}
 
 l_noret luaD_throw (lua_State *L, int errcode) {
   if (L->errorJmp) {  /* thread has an error handler? */
diff --git a/luprex/ext/eris-master/src/lua.h b/luprex/ext/eris-master/src/lua.h
index 165d685d..385e9175 100644
--- a/luprex/ext/eris-master/src/lua.h
+++ b/luprex/ext/eris-master/src/lua.h
@@ -150,6 +150,7 @@ LUA_API void  (lua_insert) (lua_State *L, int idx);
 LUA_API void  (lua_replace) (lua_State *L, int idx);
 LUA_API void  (lua_copy) (lua_State *L, int fromidx, int toidx);
 LUA_API int   (lua_checkstack) (lua_State *L, int sz);
+LUA_API int   (lua_isthrowing) (lua_State *L);
 
 LUA_API void  (lua_xmove) (lua_State *from, lua_State *to, int n);