diff --git a/HISTORY b/HISTORY
index 0253cf7..bec2b45 100755
--- a/HISTORY
+++ b/HISTORY
@@ -1,3 +1,6 @@
+May. 8 2017
+Added a global alive object checker
+
 May. 7 2017
 Fixed a wrong context processing bug when evaluating a routine manually, thanks to Diederik for pointing it out
 
diff --git a/MY-BASIC Quick Reference.pdf b/MY-BASIC Quick Reference.pdf
index f482385..0444c6c 100644
Binary files a/MY-BASIC Quick Reference.pdf and b/MY-BASIC Quick Reference.pdf differ
diff --git a/core/my_basic.c b/core/my_basic.c
index 567b7cc..6fd54b5 100755
--- a/core/my_basic.c
+++ b/core/my_basic.c
@@ -411,7 +411,7 @@ typedef struct _usertype_ref_t {
 	mb_cmp_func_t cmp;
 	mb_fmt_func_t fmt;
 #ifdef MB_ENABLE_ALIVE_CHECKING_ON_USERTYPE_REF
-	mb_alive_checker alive_checker;
+	mb_alive_value_checker alive_checker;
 #endif /* MB_ENABLE_ALIVE_CHECKING_ON_USERTYPE_REF */
 	_calculation_operator_info_t* calc_operators;
 	mb_meta_func_t coll_func;
@@ -869,6 +869,7 @@ typedef struct mb_interpreter_t {
 	unsigned short last_error_row;
 	unsigned short last_error_col;
 	/** Handlers */
+	mb_alive_checker alive_check_handler;
 	mb_debug_stepped_handler_t debug_stepped_handler;
 	mb_error_handler_t error_handler;
 	mb_print_func_t printer;
@@ -6537,6 +6538,8 @@ static void _gc_collect_garbage(mb_interpreter_t* s, int depth) {
 	if(depth != -1)
 		gc->valid_table = valid;
 	_gc_get_reachable(s, valid);
+	if(s->alive_check_handler)
+		s->alive_check_handler(s, valid, _gc_alive_marker);
 
 	/* Get unreachable information */
 	_HT_FOREACH(valid, _do_nothing_on_object, _ht_remove_exist, gc->table);
@@ -12727,8 +12730,20 @@ _exit:
 	return result;
 }
 
+/* Set the global alive checker */
+int mb_set_alive_checker(struct mb_interpreter_t* s, mb_alive_checker f) {
+	int result = MB_FUNC_OK;
+
+	if(!s)
+		result = MB_FUNC_ERR;
+	else
+		s->alive_check_handler = f;
+
+	return result;
+}
+
 /* Set the alive checker of a value */
-int mb_set_alive_checker_of_value(struct mb_interpreter_t* s, void** l, mb_value_t val, mb_alive_checker f) {
+int mb_set_alive_checker_of_value(struct mb_interpreter_t* s, void** l, mb_value_t val, mb_alive_value_checker f) {
 #ifdef MB_ENABLE_ALIVE_CHECKING_ON_USERTYPE_REF
 	int result = MB_FUNC_OK;
 	_object_t obj;
@@ -17737,6 +17752,7 @@ static int _coll_move_next(mb_interpreter_t* s, void** l) {
 	mb_value_t it;
 	_object_t oit;
 	mb_value_t ret;
+	mb_meta_status_u os = MB_MS_NONE;
 
 	mb_assert(s && l);
 
@@ -17746,43 +17762,47 @@ static int _coll_move_next(mb_interpreter_t* s, void** l) {
 	mb_check(mb_attempt_open_bracket(s, l));
 
 	mb_check(mb_pop_value(s, l, &it));
+	os = _try_overridden(s, l, &it, _COLL_ID_MOVE_NEXT, MB_MF_COLL);
+	if((os & MB_MS_DONE) == MB_MS_NONE) {
+		_MAKE_NIL(&oit);
+		switch(it.type) {
+		case MB_DT_LIST_IT:
+			_public_value_to_internal_object(&it, &oit);
+			oit.data.list_it = _move_list_it_next(oit.data.list_it);
+			if(_invalid_list_it(oit.data.list_it)) {
+				_handle_error_on_obj(s, SE_RN_INVALID_ITERATOR, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
+			} else if(oit.data.list_it) {
+				mb_make_bool(ret, true);
+			} else {
+				mb_make_nil(ret);
+			}
+
+			break;
+		case MB_DT_DICT_IT:
+			_public_value_to_internal_object(&it, &oit);
+			oit.data.dict_it = _move_dict_it_next(oit.data.dict_it);
+			if(_invalid_dict_it(oit.data.dict_it)) {
+				_handle_error_on_obj(s, SE_RN_INVALID_ITERATOR, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
+			} else if(oit.data.dict_it) {
+				mb_make_bool(ret, true);
+			} else {
+				mb_make_nil(ret);
+			}
+
+			break;
+		default:
+			_handle_error_on_obj(s, SE_RN_ITERATOR_EXPECTED, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
+
+			break;
+		}
+	}
 
 	mb_check(mb_attempt_close_bracket(s, l));
 
-	_MAKE_NIL(&oit);
-	switch(it.type) {
-	case MB_DT_LIST_IT:
-		_public_value_to_internal_object(&it, &oit);
-		oit.data.list_it = _move_list_it_next(oit.data.list_it);
-		if(_invalid_list_it(oit.data.list_it)) {
-			_handle_error_on_obj(s, SE_RN_INVALID_ITERATOR, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
-		} else if(oit.data.list_it) {
-			mb_make_bool(ret, true);
-		} else {
-			mb_make_nil(ret);
-		}
-
-		break;
-	case MB_DT_DICT_IT:
-		_public_value_to_internal_object(&it, &oit);
-		oit.data.dict_it = _move_dict_it_next(oit.data.dict_it);
-		if(_invalid_dict_it(oit.data.dict_it)) {
-			_handle_error_on_obj(s, SE_RN_INVALID_ITERATOR, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
-		} else if(oit.data.dict_it) {
-			mb_make_bool(ret, true);
-		} else {
-			mb_make_nil(ret);
-		}
-
-		break;
-	default:
-		_handle_error_on_obj(s, SE_RN_ITERATOR_EXPECTED, s->source_file, DON2(l), MB_FUNC_ERR, _exit, result);
-
-		break;
+	if((os & MB_MS_RETURNED) == MB_MS_NONE) {
+		mb_check(mb_push_value(s, l, ret));
 	}
 
-	mb_check(mb_push_value(s, l, ret));
-
 _exit:
 	return result;
 }
diff --git a/core/my_basic.h b/core/my_basic.h
index d5f20a9..903c08c 100755
--- a/core/my_basic.h
+++ b/core/my_basic.h
@@ -563,7 +563,8 @@ typedef unsigned (* mb_hash_func_t)(struct mb_interpreter_t*, void*);
 typedef int (* mb_cmp_func_t)(struct mb_interpreter_t*, void*, void*);
 typedef int (* mb_fmt_func_t)(struct mb_interpreter_t*, void*, char*, unsigned);
 typedef void (* mb_alive_marker)(struct mb_interpreter_t*, void*, mb_value_t);
-typedef void (* mb_alive_checker)(struct mb_interpreter_t*, void*, mb_value_t, mb_alive_marker);
+typedef void (* mb_alive_checker)(struct mb_interpreter_t*, void*, mb_alive_marker);
+typedef void (* mb_alive_value_checker)(struct mb_interpreter_t*, void*, mb_value_t, mb_alive_marker);
 typedef int (* mb_meta_operator_t)(struct mb_interpreter_t*, void**, mb_value_t*, mb_value_t*, mb_value_t*);
 typedef mb_meta_status_u (* mb_meta_func_t)(struct mb_interpreter_t*, void**, mb_value_t*, const char*);
 typedef char* (* mb_memory_allocate_func_t)(unsigned);
@@ -623,7 +624,8 @@ MBAPI int mb_make_ref_value(struct mb_interpreter_t* s, void* val, mb_value_t* o
 MBAPI int mb_get_ref_value(struct mb_interpreter_t* s, void** l, mb_value_t val, void** out);
 MBAPI int mb_ref_value(struct mb_interpreter_t* s, void** l, mb_value_t val);
 MBAPI int mb_unref_value(struct mb_interpreter_t* s, void** l, mb_value_t val);
-MBAPI int mb_set_alive_checker_of_value(struct mb_interpreter_t* s, void** l, mb_value_t val, mb_alive_checker f);
+MBAPI int mb_set_alive_checker(struct mb_interpreter_t* s, mb_alive_checker f);
+MBAPI int mb_set_alive_checker_of_value(struct mb_interpreter_t* s, void** l, mb_value_t val, mb_alive_value_checker f);
 MBAPI int mb_override_value(struct mb_interpreter_t* s, void** l, mb_value_t val, mb_meta_func_u m, void* f);
 MBAPI int mb_dispose_value(struct mb_interpreter_t* s, mb_value_t val);