diff --git a/docs/quick-start/interop.md b/docs/quick-start/interop.md
index b98b9819..0183b5c0 100644
--- a/docs/quick-start/interop.md
+++ b/docs/quick-start/interop.md
@@ -39,4 +39,5 @@ std::cout << CAST(Str, i);	// abc
 
 + `is_type(PyObject* obj, Type type)`
 + `is_non_tagged_type(PyObject* obj, Type type)`
-+ `VM::check_type(PyObject* obj, Type type)`
\ No newline at end of file
++ `VM::check_type(PyObject* obj, Type type)`
++ `VM::check_non_tagged_type(PyObject* obj, Type type)`
\ No newline at end of file
diff --git a/src/ceval.h b/src/ceval.h
index bd5a4197..969a886a 100644
--- a/src/ceval.h
+++ b/src/ceval.h
@@ -487,7 +487,7 @@ __NEXT_STEP:;
         StrName name(byte.arg);
         PyObject* super_cls = POPX();
         if(super_cls == None) super_cls = _t(tp_object);
-        check_type(super_cls, tp_type);
+        check_non_tagged_type(super_cls, tp_type);
         PyObject* cls = new_type_object(frame->_module, name, OBJ_GET(Type, super_cls));
         PUSH(cls);
     } DISPATCH();
diff --git a/src/pocketpy.h b/src/pocketpy.h
index aee2d6c1..2dd32c80 100644
--- a/src/pocketpy.h
+++ b/src/pocketpy.h
@@ -68,7 +68,7 @@ inline void init_builtins(VM* _vm) {
     });
 
     _vm->bind_builtin_func<2>("super", [](VM* vm, ArgsView args) {
-        vm->check_type(args[0], vm->tp_type);
+        vm->check_non_tagged_type(args[0], vm->tp_type);
         Type type = OBJ_GET(Type, args[0]);
         if(!vm->isinstance(args[1], type)){
             Str _0 = obj_type_name(vm, OBJ_GET(Type, vm->_t(args[1])));
@@ -80,7 +80,7 @@ inline void init_builtins(VM* _vm) {
     });
 
     _vm->bind_builtin_func<2>("isinstance", [](VM* vm, ArgsView args) {
-        vm->check_type(args[1], vm->tp_type);
+        vm->check_non_tagged_type(args[1], vm->tp_type);
         Type type = OBJ_GET(Type, args[1]);
         return VAR(vm->isinstance(args[0], type));
     });
diff --git a/src/vm.h b/src/vm.h
index 682b1569..ceb6579d 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -30,14 +30,14 @@ inline int set_read_file_cwd(ReadFileCwdFunc func) { _read_file_cwd = func; retu
 
 #define DEF_NATIVE_2(ctype, ptype)                                      \
     template<> inline ctype py_cast<ctype>(VM* vm, PyObject* obj) {     \
-        vm->check_type(obj, vm->ptype);                                 \
+        vm->check_non_tagged_type(obj, vm->ptype);                      \
         return OBJ_GET(ctype, obj);                                     \
     }                                                                   \
     template<> inline ctype _py_cast<ctype>(VM* vm, PyObject* obj) {    \
         return OBJ_GET(ctype, obj);                                     \
     }                                                                   \
     template<> inline ctype& py_cast<ctype&>(VM* vm, PyObject* obj) {   \
-        vm->check_type(obj, vm->ptype);                                 \
+        vm->check_non_tagged_type(obj, vm->ptype);                      \
         return OBJ_GET(ctype, obj);                                     \
     }                                                                   \
     template<> inline ctype& _py_cast<ctype&>(VM* vm, PyObject* obj) {  \
@@ -362,6 +362,21 @@ public:
         TypeError("expected " + OBJ_NAME(_t(type)).escape() + ", but got " + OBJ_NAME(_t(obj)).escape());
     }
 
+    void check_non_tagged_type(PyObject* obj, Type type){
+        if(is_non_tagged_type(obj, type)) return;
+        TypeError("expected " + OBJ_NAME(_t(type)).escape() + ", but got " + OBJ_NAME(_t(obj)).escape());
+    }
+
+    void check_int(PyObject* obj){
+        if(is_int(obj)) return;
+        check_type(obj, tp_int);
+    }
+
+    void check_float(PyObject* obj){
+        if(is_float(obj)) return;
+        check_type(obj, tp_float);
+    }
+
     PyObject* _t(Type t){
         return _all_types[t.index].obj;
     }
@@ -434,7 +449,7 @@ DEF_NATIVE_2(MappingProxy, tp_mappingproxy)
 
 #define PY_CAST_INT(T)                                  \
 template<> inline T py_cast<T>(VM* vm, PyObject* obj){  \
-    vm->check_type(obj, vm->tp_int);                    \
+    vm->check_int(obj);                                 \
     return (T)(BITS(obj) >> 2);                         \
 }                                                       \
 template<> inline T _py_cast<T>(VM* vm, PyObject* obj){ \
@@ -454,7 +469,7 @@ PY_CAST_INT(unsigned long long)
 
 
 template<> inline float py_cast<float>(VM* vm, PyObject* obj){
-    vm->check_type(obj, vm->tp_float);
+    vm->check_float(obj);
     i64 bits = BITS(obj);
     bits = (bits >> 2) << 2;
     return BitsCvt(bits)._float;
@@ -465,7 +480,7 @@ template<> inline float _py_cast<float>(VM* vm, PyObject* obj){
     return BitsCvt(bits)._float;
 }
 template<> inline double py_cast<double>(VM* vm, PyObject* obj){
-    vm->check_type(obj, vm->tp_float);
+    vm->check_float(obj);
     i64 bits = BITS(obj);
     bits = (bits >> 2) << 2;
     return BitsCvt(bits)._float;
@@ -515,7 +530,7 @@ inline PyObject* py_var(VM* vm, bool val){
 }
 
 template<> inline bool py_cast<bool>(VM* vm, PyObject* obj){
-    vm->check_type(obj, vm->tp_bool);
+    vm->check_non_tagged_type(obj, vm->tp_bool);
     return obj == vm->True;
 }
 template<> inline bool _py_cast<bool>(VM* vm, PyObject* obj){
@@ -536,7 +551,7 @@ inline PyObject* py_var(VM* vm, std::string_view val){
 
 template<typename T>
 void _check_py_class(VM* vm, PyObject* obj){
-    vm->check_type(obj, T::_type(vm));
+    vm->check_non_tagged_type(obj, T::_type(vm));
 }
 
 inline PyObject* VM::num_negated(PyObject* obj){
@@ -1169,7 +1184,7 @@ inline void VM::setattr(PyObject* obj, StrName name, PyObject* value){
 
 template<int ARGC>
 void VM::bind_method(PyObject* obj, Str name, NativeFuncC fn) {
-    check_type(obj, tp_type);
+    check_non_tagged_type(obj, tp_type);
     obj->attr().set(name, VAR(NativeFunc(fn, ARGC, true)));
 }