diff --git a/include/pocketpy/interpreter/types.h b/include/pocketpy/interpreter/types.h
new file mode 100644
index 00000000..eecd9497
--- /dev/null
+++ b/include/pocketpy/interpreter/types.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "pocketpy/common/vector.h"
+#include "pocketpy/objects/base.h"
+
+#define PK_DICT_MAX_COLLISION 4
+
+typedef struct {
+    uint64_t hash;
+    py_TValue key;
+    py_TValue val;
+} DictEntry;
+
+typedef struct {
+    int _[PK_DICT_MAX_COLLISION];
+} DictIndex;
+
+typedef struct {
+    int length;
+    uint32_t capacity;
+    DictIndex* indices;
+    c11_vector /*T=DictEntry*/ entries;
+} Dict;
+
+typedef c11_vector List;
diff --git a/include/pocketpy/interpreter/vm.h b/include/pocketpy/interpreter/vm.h
index 92f47cec..47b69dfe 100644
--- a/include/pocketpy/interpreter/vm.h
+++ b/include/pocketpy/interpreter/vm.h
@@ -8,6 +8,7 @@
 #include "pocketpy/interpreter/modules.h"
 #include "pocketpy/interpreter/typeinfo.h"
 #include "pocketpy/interpreter/name.h"
+#include "pocketpy/interpreter/types.h"
 
 // TODO:
 // 1. __eq__ and __ne__ fallbacks
@@ -58,7 +59,6 @@ bool pk__parse_int_slice(py_Ref slice, int length, int* restrict start, int* res
 bool pk__normalize_index(int* index, int length);
 
 #define pk__mark_value(val) if((val)->is_ptr && !(val)->_obj->gc_marked) PyObject__mark((val)->_obj)
-void pk__mark_namedict(NameDict*);
 void pk__tp_set_marker(py_Type type, void (*gc_mark)(void*));
 bool pk__object_new(int argc, py_Ref argv);
 py_TypeInfo* pk__type_info(py_Type type);
diff --git a/src/interpreter/generator.c b/src/interpreter/generator.c
index bccfe13a..82eb4d48 100644
--- a/src/interpreter/generator.c
+++ b/src/interpreter/generator.c
@@ -76,16 +76,8 @@ static bool generator__next__(int argc, py_Ref argv) {
     }
 }
 
-static void generator__gc_mark(void* ud){
-    Generator* gen = ud;
-    if(gen->frame) Frame__gc_mark(gen->frame);
-}
-
 py_Type pk_generator__register() {
     py_Type type = pk_newtype("generator", tp_object, NULL, (py_Dtor)Generator__dtor, false, true);
-
-    pk__tp_set_marker(type, generator__gc_mark);
-
     py_bindmagic(type, __iter__, pk_wrapper__self);
     py_bindmagic(type, __next__, generator__next__);
     return type;
diff --git a/src/interpreter/vm.c b/src/interpreter/vm.c
index 9e7e38df..99f934d9 100644
--- a/src/interpreter/vm.c
+++ b/src/interpreter/vm.c
@@ -604,13 +604,6 @@ void PyObject__dtor(PyObject* self) {
     if(self->slots == -1) NameDict__dtor(PyObject__dict(self));
 }
 
-void pk__mark_namedict(NameDict* dict) {
-    for(int i = 0; i < dict->length; i++) {
-        NameDict_KV* kv = c11__at(NameDict_KV, dict, i);
-        pk__mark_value(&kv->value);
-    }
-}
-
 void pk__tp_set_marker(py_Type type, void (*gc_mark)(void*)) {
     py_TypeInfo* ti = pk__type_info(type);
     assert(ti->gc_mark == NULL);
@@ -627,12 +620,42 @@ void PyObject__mark(PyObject* obj) {
         for(int i = 0; i < obj->slots; i++)
             pk__mark_value(p + i);
     } else if(obj->slots == -1) {
-        NameDict* dict = PyObject__dict(obj);
-        pk__mark_namedict(dict);
+        NameDict* namedict = PyObject__dict(obj);
+        for(int i = 0; i < namedict->length; i++) {
+            NameDict_KV* kv = c11__at(NameDict_KV, namedict, i);
+            pk__mark_value(&kv->value);
+        }
     }
 
-    py_TypeInfo* ti = pk__type_info(obj->type);
-    if(ti->gc_mark) ti->gc_mark(PyObject__userdata(obj));
+    void* ud = PyObject__userdata(obj);
+    switch(obj->type) {
+        case tp_list: {
+            List* self = ud;
+            for(int i = 0; i < self->length; i++) {
+                pk__mark_value(c11__at(py_TValue, self, i));
+            }
+            break;
+        }
+        case tp_dict: {
+            Dict* self = ud;
+            for(int i = 0; i < self->entries.length; i++) {
+                DictEntry* entry = c11__at(DictEntry, &self->entries, i);
+                if(py_isnil(&entry->key)) continue;
+                pk__mark_value(&entry->key);
+                pk__mark_value(&entry->val);
+            }
+            break;
+        }
+        case tp_generator: {
+            Generator* self = ud;
+            if(self->frame) Frame__gc_mark(self->frame);
+            break;
+        }
+        default: {
+            py_TypeInfo* ti = pk__type_info(obj->type);
+            if(ti->gc_mark) ti->gc_mark(ud);
+        }
+    }
 }
 
 void FuncDecl__gc_mark(const FuncDecl* self) {
diff --git a/src/public/modules.c b/src/public/modules.c
index b165dd16..98953daa 100644
--- a/src/public/modules.c
+++ b/src/public/modules.c
@@ -776,7 +776,13 @@ py_TValue pk_builtins__register() {
 static void function__gc_mark(void* ud) {
     Function* func = ud;
     if(func->globals) pk__mark_value(func->globals);
-    if(func->closure) pk__mark_namedict(func->closure);
+    if(func->closure) {
+        NameDict* namedict = func->closure;
+        for(int i = 0; i < namedict->length; i++) {
+            NameDict_KV* kv = c11__at(NameDict_KV, namedict, i);
+            pk__mark_value(&kv->value);
+        }
+    }
     FuncDecl__gc_mark(func->decl);
 }
 
diff --git a/src/public/py_dict.c b/src/public/py_dict.c
index 8f12f476..4ab786c8 100644
--- a/src/public/py_dict.c
+++ b/src/public/py_dict.c
@@ -5,8 +5,6 @@
 #include "pocketpy/objects/object.h"
 #include "pocketpy/interpreter/vm.h"
 
-#define PK_DICT_MAX_COLLISION 4
-
 static uint32_t Dict__next_cap(uint32_t cap) {
     switch(cap) {
         case 7: return 17;
@@ -53,22 +51,7 @@ static uint32_t Dict__next_cap(uint32_t cap) {
     }
 }
 
-typedef struct {
-    uint64_t hash;
-    py_TValue key;
-    py_TValue val;
-} DictEntry;
 
-typedef struct {
-    int _[PK_DICT_MAX_COLLISION];
-} DictIndex;
-
-typedef struct {
-    int length;
-    uint32_t capacity;
-    DictIndex* indices;
-    c11_vector /*T=DictEntry*/ entries;
-} Dict;
 
 typedef struct {
     DictEntry* curr;
@@ -525,21 +508,9 @@ static bool dict_values(int argc, py_Ref argv) {
     return true;
 }
 
-static void dict__gc_mark(void* ud) {
-    Dict* self = ud;
-    for(int i = 0; i < self->entries.length; i++) {
-        DictEntry* entry = c11__at(DictEntry, &self->entries, i);
-        if(py_isnil(&entry->key)) continue;
-        pk__mark_value(&entry->key);
-        pk__mark_value(&entry->val);
-    }
-}
-
 py_Type pk_dict__register() {
     py_Type type = pk_newtype("dict", tp_object, NULL, (void (*)(void*))Dict__dtor, false, false);
 
-    pk__tp_set_marker(type, dict__gc_mark);
-
     py_bindmagic(type, __new__, dict__new__);
     py_bindmagic(type, __init__, dict__init__);
     py_bindmagic(type, __getitem__, dict__getitem__);
diff --git a/src/public/py_list.c b/src/public/py_list.c
index 904653f1..d33585cf 100644
--- a/src/public/py_list.c
+++ b/src/public/py_list.c
@@ -5,8 +5,6 @@
 #include "pocketpy/interpreter/vm.h"
 #include "pocketpy/common/sstream.h"
 
-typedef c11_vector List;
-
 void py_newlist(py_Ref out) {
     List* ud = py_newobject(out, tp_list, 0, sizeof(List));
     c11_vector__ctor(ud, sizeof(py_TValue));
@@ -404,19 +402,10 @@ static bool list__contains__(int argc, py_Ref argv) {
     return pk_arraycontains(py_arg(0), py_arg(1));
 }
 
-static void list__gc_mark(void* ud) {
-    List* self = ud;
-    for(int i = 0; i < self->length; i++) {
-        pk__mark_value(c11__at(py_TValue, self, i));
-    }
-}
-
 py_Type pk_list__register() {
     py_Type type =
         pk_newtype("list", tp_object, NULL, (void (*)(void*))c11_vector__dtor, false, true);
 
-    pk__tp_set_marker(type, list__gc_mark);
-
     py_bindmagic(type, __len__, list__len__);
     py_bindmagic(type, __eq__, list__eq__);
     py_bindmagic(type, __ne__, list__ne__);