diff --git a/crates/stdlib/src/array.rs b/crates/stdlib/src/array.rs
index 4fcba1f872..49ca4a8903 100644
--- a/crates/stdlib/src/array.rs
+++ b/crates/stdlib/src/array.rs
@@ -1399,7 +1399,7 @@ mod array {
         internal: PyMutex<PositionIterInternal<PyArrayRef>>,
     }
 
-    #[pyclass(with(IterNext, Iterable), flags(HAS_DICT))]
+    #[pyclass(with(IterNext, Iterable), flags(HAS_DICT, DISALLOW_INSTANTIATION))]
     impl PyArrayIter {
         #[pymethod]
         fn __setstate__(&self, state: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
diff --git a/crates/stdlib/src/csv.rs b/crates/stdlib/src/csv.rs
index 3c7cc2ff80..792402e058 100644
--- a/crates/stdlib/src/csv.rs
+++ b/crates/stdlib/src/csv.rs
@@ -908,7 +908,7 @@ mod _csv {
         }
     }
 
-    #[pyclass(with(IterNext, Iterable))]
+    #[pyclass(with(IterNext, Iterable), flags(DISALLOW_INSTANTIATION))]
     impl Reader {
         #[pygetset]
         fn line_num(&self) -> u64 {
@@ -1059,7 +1059,7 @@ mod _csv {
         }
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl Writer {
         #[pygetset(name = "dialect")]
         const fn get_dialect(&self, _vm: &VirtualMachine) -> PyDialect {
diff --git a/crates/stdlib/src/pystruct.rs b/crates/stdlib/src/pystruct.rs
index 798e5f5de8..a238a5d077 100644
--- a/crates/stdlib/src/pystruct.rs
+++ b/crates/stdlib/src/pystruct.rs
@@ -189,7 +189,7 @@ pub(crate) mod _struct {
         }
     }
 
-    #[pyclass(with(Unconstructible, IterNext, Iterable))]
+    #[pyclass(with(IterNext, Iterable), flags(DISALLOW_INSTANTIATION))]
     impl UnpackIterator {
         #[pymethod]
         fn __length_hint__(&self) -> usize {
diff --git a/crates/stdlib/src/unicodedata.rs b/crates/stdlib/src/unicodedata.rs
index 46e1835726..68d9a17e57 100644
--- a/crates/stdlib/src/unicodedata.rs
+++ b/crates/stdlib/src/unicodedata.rs
@@ -105,7 +105,7 @@ mod unicodedata {
         }
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl Ucd {
         #[pymethod]
         fn category(&self, character: PyStrRef, vm: &VirtualMachine) -> PyResult<String> {
diff --git a/crates/stdlib/src/zlib.rs b/crates/stdlib/src/zlib.rs
index 328452ae9d..9ca94939f7 100644
--- a/crates/stdlib/src/zlib.rs
+++ b/crates/stdlib/src/zlib.rs
@@ -225,7 +225,7 @@ mod zlib {
         inner: PyMutex<PyDecompressInner>,
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl PyDecompress {
         #[pygetset]
         fn eof(&self) -> bool {
@@ -383,7 +383,7 @@ mod zlib {
         inner: PyMutex<CompressState<CompressInner>>,
     }
 
-    #[pyclass]
+    #[pyclass(flags(DISALLOW_INSTANTIATION))]
     impl PyCompress {
         #[pymethod]
         fn compress(&self, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
diff --git a/crates/vm/src/builtins/type.rs b/crates/vm/src/builtins/type.rs
index 0f619b1399..457b239a6f 100644
--- a/crates/vm/src/builtins/type.rs
+++ b/crates/vm/src/builtins/type.rs
@@ -401,6 +401,8 @@ impl PyType {
             None,
         );
 
+        Self::set_new(&new_type.slots, &new_type.base);
+
         let weakref_type = super::PyWeak::static_type();
         for base in new_type.bases.read().iter() {
             base.subclasses.write().push(
@@ -420,9 +422,6 @@ impl PyType {
 
         for cls in self.mro.read().iter() {
             for &name in cls.attributes.read().keys() {
-                if name == identifier!(ctx, __new__) {
-                    continue;
-                }
                 if name.as_bytes().starts_with(b"__") && name.as_bytes().ends_with(b"__") {
                     slot_name_set.insert(name);
                 }
@@ -436,6 +435,31 @@ impl PyType {
         for attr_name in slot_name_set {
             self.update_slot::<true>(attr_name, ctx);
         }
+
+        Self::set_new(&self.slots, &self.base);
+    }
+
+    fn set_new(slots: &PyTypeSlots, base: &Option<PyTypeRef>) {
+        // if self.slots.new.load().is_none()
+        //     && self
+        //         .base
+        //         .as_ref()
+        //         .map(|base| base.class().is(ctx.types.object_type))
+        //         .unwrap_or(false)
+        //     && self.slots.flags.contains(PyTypeFlags::HEAPTYPE)
+        // {
+        //     self.slots.flags |= PyTypeFlags::DISALLOW_INSTANTIATION;
+        // }
+
+        if slots.flags.contains(PyTypeFlags::DISALLOW_INSTANTIATION) {
+            slots.new.store(None)
+        } else if slots.new.load().is_none() {
+            slots.new.store(
+                base.as_ref()
+                    .map(|base| base.slots.new.load())
+                    .unwrap_or(None),
+            )
+        }
     }
 
     // This is used for class initialization where the vm is not yet available.
@@ -1563,15 +1587,28 @@ impl Callable for PyType {
     type Args = FuncArgs;
     fn call(zelf: &Py<Self>, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
         vm_trace!("type_call: {:?}", zelf);
-        let obj = call_slot_new(zelf.to_owned(), zelf.to_owned(), args.clone(), vm)?;
 
-        if (zelf.is(vm.ctx.types.type_type) && args.kwargs.is_empty()) || !obj.fast_isinstance(zelf)
-        {
+        if zelf.is(vm.ctx.types.type_type) {
+            let num_args = args.args.len();
+            if num_args == 1 && args.kwargs.is_empty() {
+                return Ok(args.args[0].obj_type());
+            }
+            if num_args != 3 {
+                return Err(vm.new_type_error("type() takes 1 or 3 arguments".to_owned()));
+            }
+        }
+
+        let obj = if let Some(slot_new) = zelf.slots.new.load() {
+            slot_new(zelf.to_owned(), args.clone(), vm)?
+        } else {
+            return Err(vm.new_type_error(format!("cannot create '{}' instances", zelf.slots.name)));
+        };
+
+        if !obj.class().fast_issubclass(zelf) {
             return Ok(obj);
         }
 
-        let init = obj.class().mro_find_map(|cls| cls.slots.init.load());
-        if let Some(init_method) = init {
+        if let Some(init_method) = obj.class().slots.init.load() {
             init_method(obj.clone(), args, vm)?;
         }
         Ok(obj)