diff --git a/include/pocketpy/objects/codeobject.h b/include/pocketpy/objects/codeobject.h
index 220cb8cc..b66b1eb7 100644
--- a/include/pocketpy/objects/codeobject.h
+++ b/include/pocketpy/objects/codeobject.h
@@ -120,15 +120,16 @@ void FuncDecl__add_arg(FuncDecl* self, py_Name name);
 void FuncDecl__add_kwarg(FuncDecl* self, py_Name name, const py_TValue* value);
 void FuncDecl__add_starred_arg(FuncDecl* self, py_Name name);
 void FuncDecl__add_starred_kwarg(FuncDecl* self, py_Name name);
+void FuncDecl__gc_mark(const FuncDecl* self);
 
 // runtime function
 typedef struct Function {
     FuncDecl_ decl;
     py_TValue module;      // weak ref
     PyObject* clazz;       // weak ref
-    NameDict* closure;  // strong ref
+    NameDict* closure;     // strong ref
     py_CFunction cfunc;    // wrapped C function
 } Function;
 
 void Function__ctor(Function* self, FuncDecl_ decl, py_TValue* module);
-void Function__dtor(Function* self);
\ No newline at end of file
+void Function__dtor(Function* self);
diff --git a/src/interpreter/vm.c b/src/interpreter/vm.c
index 6b6108f6..fed282c8 100644
--- a/src/interpreter/vm.c
+++ b/src/interpreter/vm.c
@@ -602,6 +602,14 @@ static void mark_object(PyObject* obj) {
     if(ti->gc_mark) ti->gc_mark(PyObject__userdata(obj));
 }
 
+void FuncDecl__gc_mark(const FuncDecl* self) {
+    CodeObject__gc_mark(&self->code);
+    for(int j = 0; j < self->kwargs.length; j++) {
+        FuncDeclKwArg* kw = c11__at(FuncDeclKwArg, &self->kwargs, j);
+        pk__mark_value(&kw->value);
+    }
+}
+
 void CodeObject__gc_mark(const CodeObject* self) {
     for(int i = 0; i < self->consts.length; i++) {
         py_TValue* p = c11__at(py_TValue, &self->consts, i);
@@ -609,12 +617,7 @@ void CodeObject__gc_mark(const CodeObject* self) {
     }
     for(int i = 0; i < self->func_decls.length; i++) {
         FuncDecl_ decl = c11__getitem(FuncDecl_, &self->func_decls, i);
-        CodeObject__gc_mark(&decl->code);
-
-        for(int j = 0; j < decl->kwargs.length; j++) {
-            FuncDeclKwArg* kw = c11__at(FuncDeclKwArg, &decl->kwargs, j);
-            pk__mark_value(&kw->value);
-        }
+        FuncDecl__gc_mark(decl);
     }
 }
 
diff --git a/src/public/modules.c b/src/public/modules.c
index e2fda4a7..d5d82ec1 100644
--- a/src/public/modules.c
+++ b/src/public/modules.c
@@ -685,7 +685,7 @@ py_TValue pk_builtins__register() {
 static void function__gc_mark(void* ud) {
     Function* func = ud;
     if(func->closure) pk__mark_namedict(func->closure);
-    CodeObject__gc_mark(&func->decl->code);
+    FuncDecl__gc_mark(func->decl);
 }
 
 static bool function__doc__(int argc, py_Ref argv) {