diff --git a/derive/src/pyclass.rs b/derive/src/pyclass.rs
index f06e66408..bc0869c14 100644
--- a/derive/src/pyclass.rs
+++ b/derive/src/pyclass.rs
@@ -345,8 +345,10 @@ where
             match slot_name.as_str() {
                 "call" => quote! {
                     slots.#slot_ident.store(Some(
-                        |vm: &::rustpython_vm::VirtualMachine, args: ::rustpython_vm::function::PyFuncArgs| -> ::rustpython_vm::pyobject::PyResult {
-                            ::rustpython_vm::function::IntoPyNativeFunc::call(&Self::#ident, vm, args)
+                        |zelf: ::rustpython_vm::pyobject::PyObjectRef,  args: ::rustpython_vm::function::PyFuncArgs, vm: &::rustpython_vm::VirtualMachine| -> ::rustpython_vm::pyobject::PyResult {
+                            use ::rustpython_vm::pyobject::TryFromObject;
+                            let zelf = PyRef::<Self>::try_from_object(vm, zelf)?;
+                            Self::#ident(zelf, args, vm)
                         } as _
                     ));
                 },
diff --git a/vm/src/obj/objbuiltinfunc.rs b/vm/src/obj/objbuiltinfunc.rs
index 2c7206f81..acc46aab9 100644
--- a/vm/src/obj/objbuiltinfunc.rs
+++ b/vm/src/obj/objbuiltinfunc.rs
@@ -1,7 +1,7 @@
 use std::fmt;
 
 use super::objclassmethod::PyClassMethod;
-use crate::function::{OptionalArg, PyFuncArgs, PyNativeFunc};
+use crate::function::{PyFuncArgs, PyNativeFunc};
 use crate::obj::objstr::PyStringRef;
 use crate::obj::objtype::PyClassRef;
 use crate::pyobject::{
@@ -169,10 +169,10 @@ impl PyBuiltinMethod {
 
 impl SlotDescriptor for PyBuiltinMethod {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        cls: OptionalArg<PyObjectRef>,
+        cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = match Self::_check(zelf, obj, vm) {
             Ok(obj) => obj,
diff --git a/vm/src/obj/objclassmethod.rs b/vm/src/obj/objclassmethod.rs
index d69b85a96..3c9d8e6e4 100644
--- a/vm/src/obj/objclassmethod.rs
+++ b/vm/src/obj/objclassmethod.rs
@@ -1,5 +1,4 @@
 use super::objtype::PyClassRef;
-use crate::function::OptionalArg;
 use crate::pyobject::{
     PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
 };
@@ -47,10 +46,10 @@ impl PyValue for PyClassMethod {
 
 impl SlotDescriptor for PyClassMethod {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        cls: OptionalArg<PyObjectRef>,
+        cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = Self::_unwrap(zelf, obj, vm)?;
         let cls = cls.unwrap_or_else(|| obj.class().into_object());
diff --git a/vm/src/obj/objfunction.rs b/vm/src/obj/objfunction.rs
index a7ecdb9ee..646f2d411 100644
--- a/vm/src/obj/objfunction.rs
+++ b/vm/src/obj/objfunction.rs
@@ -8,7 +8,7 @@ use super::objtuple::PyTupleRef;
 use super::objtype::PyClassRef;
 use crate::bytecode;
 use crate::frame::Frame;
-use crate::function::{OptionalArg, PyFuncArgs};
+use crate::function::PyFuncArgs;
 use crate::obj::objasyncgenerator::PyAsyncGen;
 use crate::obj::objcoroutine::PyCoroutine;
 use crate::obj::objgenerator::PyGenerator;
@@ -306,10 +306,10 @@ impl PyFunction {
 
 impl SlotDescriptor for PyFunction {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        cls: OptionalArg<PyObjectRef>,
+        cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = Self::_unwrap(zelf, obj, vm)?;
         if vm.is_none(&obj) && !Self::_cls_is(&cls, &obj.class()) {
diff --git a/vm/src/obj/objgetset.rs b/vm/src/obj/objgetset.rs
index a3986efcb..c575434af 100644
--- a/vm/src/obj/objgetset.rs
+++ b/vm/src/obj/objgetset.rs
@@ -2,7 +2,7 @@
 
 */
 use super::objtype::PyClassRef;
-use crate::function::{OptionalArg, OwnedParam, RefParam};
+use crate::function::{OwnedParam, RefParam};
 use crate::pyobject::{
     IntoPyResult, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
     TypeProtocol,
@@ -182,10 +182,10 @@ pub type PyGetSetRef = PyRef<PyGetSet>;
 
 impl SlotDescriptor for PyGetSet {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        _cls: OptionalArg<PyObjectRef>,
+        _cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = match Self::_check(zelf, obj, vm) {
             Ok(obj) => obj,
diff --git a/vm/src/obj/objproperty.rs b/vm/src/obj/objproperty.rs
index 5af26b89d..03768f1e7 100644
--- a/vm/src/obj/objproperty.rs
+++ b/vm/src/obj/objproperty.rs
@@ -4,7 +4,6 @@
 use crate::common::cell::PyRwLock;
 
 use super::objtype::PyClassRef;
-use crate::function::OptionalArg;
 use crate::pyobject::{
     PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
 };
@@ -74,10 +73,10 @@ struct PropertyArgs {
 
 impl SlotDescriptor for PyProperty {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        _cls: OptionalArg<PyObjectRef>,
+        _cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = Self::_unwrap(zelf, obj, vm)?;
         if vm.is_none(&obj) {
diff --git a/vm/src/obj/objstaticmethod.rs b/vm/src/obj/objstaticmethod.rs
index b8fbedf25..7d32e37a6 100644
--- a/vm/src/obj/objstaticmethod.rs
+++ b/vm/src/obj/objstaticmethod.rs
@@ -1,5 +1,4 @@
 use super::objtype::PyClassRef;
-use crate::function::OptionalArg;
 use crate::pyobject::{PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue};
 use crate::slots::SlotDescriptor;
 use crate::vm::VirtualMachine;
@@ -19,10 +18,10 @@ impl PyValue for PyStaticMethod {
 
 impl SlotDescriptor for PyStaticMethod {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         _obj: Option<PyObjectRef>,
-        _cls: OptionalArg<PyObjectRef>,
+        _cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let zelf = Self::_zelf(zelf, vm)?;
         Ok(zelf.callable.clone())
diff --git a/vm/src/obj/objsuper.rs b/vm/src/obj/objsuper.rs
index 5438f2dcb..441cc5612 100644
--- a/vm/src/obj/objsuper.rs
+++ b/vm/src/obj/objsuper.rs
@@ -132,10 +132,10 @@ impl PySuper {
 
 impl SlotDescriptor for PySuper {
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        _cls: OptionalArg<PyObjectRef>,
+        _cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult {
         let (zelf, obj) = Self::_unwrap(zelf, obj, vm)?;
         if vm.is_none(&obj) || zelf.obj.is_some() {
diff --git a/vm/src/obj/objtype.rs b/vm/src/obj/objtype.rs
index e50d22dd3..6731352bc 100644
--- a/vm/src/obj/objtype.rs
+++ b/vm/src/obj/objtype.rs
@@ -11,7 +11,7 @@ use super::objstaticmethod::PyStaticMethod;
 use super::objstr::PyStringRef;
 use super::objtuple::PyTuple;
 use super::objweakref::PyWeak;
-use crate::function::{KwArgs, OptionalArg, PyFuncArgs};
+use crate::function::{KwArgs, PyFuncArgs};
 use crate::pyobject::{
     BorrowValue, IdProtocol, PyAttributes, PyClassImpl, PyContext, PyIterable, PyLease,
     PyObjectRef, PyRef, PyResult, PyValue, TryFromObject, TypeProtocol,
@@ -214,12 +214,7 @@ impl PyClass {
                     PyLease::into_pyref(attr_class).first_in_mro(|cls| cls.slots.descr_get.load())
                 {
                     let mcl = PyLease::into_pyref(mcl).into_object();
-                    return descr_get(
-                        vm,
-                        attr,
-                        Some(zelf.into_object()),
-                        OptionalArg::Present(mcl),
-                    );
+                    return descr_get(attr, Some(zelf.into_object()), Some(mcl), vm);
                 }
             }
         }
@@ -228,7 +223,7 @@ impl PyClass {
             let attr_class = attr.class();
             if let Some(ref descr_get) = attr_class.first_in_mro(|cls| cls.slots.descr_get.load()) {
                 drop(mcl);
-                return descr_get(vm, attr, None, OptionalArg::Present(zelf.into_object()));
+                return descr_get(attr, None, Some(zelf.into_object()), vm);
             }
         }
 
diff --git a/vm/src/slots.rs b/vm/src/slots.rs
index cd2297f9d..c8b59e05f 100644
--- a/vm/src/slots.rs
+++ b/vm/src/slots.rs
@@ -2,7 +2,7 @@ use std::cmp::Ordering;
 
 use crate::common::cell::PyRwLock;
 use crate::common::hash::PyHash;
-use crate::function::{IntoPyNativeFunc, OptionalArg, PyFuncArgs, PyNativeFunc};
+use crate::function::{OptionalArg, PyFuncArgs, PyNativeFunc};
 use crate::pyobject::{
     IdProtocol, PyComparisonValue, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
     TypeProtocol,
@@ -41,9 +41,9 @@ impl Default for PyTpFlags {
     }
 }
 
-type GenericFunc = fn(&VirtualMachine, PyFuncArgs) -> PyResult;
+type GenericMethod = fn(PyObjectRef, PyFuncArgs, &VirtualMachine) -> PyResult;
 type DescrGetFunc =
-    fn(&VirtualMachine, PyObjectRef, Option<PyObjectRef>, OptionalArg<PyObjectRef>) -> PyResult;
+    fn(PyObjectRef, Option<PyObjectRef>, Option<PyObjectRef>, &VirtualMachine) -> PyResult;
 type HashFunc = Box<py_dyn_fn!(dyn Fn(PyObjectRef, &VirtualMachine) -> PyResult<PyHash>)>;
 
 #[derive(Default)]
@@ -51,7 +51,7 @@ pub struct PyClassSlots {
     pub flags: PyTpFlags,
     pub name: PyRwLock<Option<String>>, // tp_name, not class name
     pub new: Option<PyNativeFunc>,
-    pub call: AtomicCell<Option<GenericFunc>>,
+    pub call: AtomicCell<Option<GenericMethod>>,
     pub descr_get: AtomicCell<Option<DescrGetFunc>>,
     pub hash: Option<HashFunc>,
     pub cmp: Option<CmpFunc>,
@@ -80,13 +80,21 @@ impl PyClassSlots {
     pub(crate) fn update_slot_func(&self, name: &str) {
         match name {
             "__call__" => {
-                let func: GenericFunc =
-                    |vm, args| { IntoPyNativeFunc::call(&call_magic_call, vm, args) } as _;
+                let func: GenericMethod = |zelf, args, vm| {
+                    let magic = get_class_magic(&zelf, "__call__");
+                    let magic = vm.call_if_get_descriptor(magic, zelf.clone())?;
+                    vm.invoke(&magic, args)
+                } as _;
                 self.call.store(Some(func))
             }
             "__get__" => {
-                let func: DescrGetFunc =
-                    |vm, zelf, obj, cls| { call_magic_descr_get(vm, zelf, obj, cls) } as _;
+                let func: DescrGetFunc = |zelf, obj, cls, vm| {
+                    let magic = get_class_magic(&zelf, "__get__");
+                    vm.invoke(
+                        &magic,
+                        vec![zelf, vm.unwrap_or_none(obj), vm.unwrap_or_none(cls)],
+                    )
+                } as _;
                 self.descr_get.store(Some(func))
             }
             _ => (),
@@ -94,6 +102,16 @@ impl PyClassSlots {
     }
 }
 
+#[inline]
+fn get_class_magic(zelf: &PyObjectRef, name: &str) -> PyObjectRef {
+    zelf.get_class_attr(name).unwrap()
+
+    // TODO: we already looked up the matching class but lost the information here
+    // let cls = zelf.lease_class();
+    // let attrs = cls.attributes.read();
+    // attrs.get(name).unwrap().clone()
+}
+
 impl std::fmt::Debug for PyClassSlots {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("PyClassSlots")
@@ -107,53 +125,14 @@ pub trait SlotCall: PyValue {
     fn call(zelf: PyRef<Self>, args: PyFuncArgs, vm: &VirtualMachine) -> PyResult;
 }
 
-#[inline]
-fn get_class_magic(zelf: &PyObjectRef, name: &str) -> PyObjectRef {
-    zelf.get_class_attr(name).unwrap()
-    // let cls = zelf.lease_class();
-    // let attrs = cls.attributes.read();
-    // let attr = attrs.get(name);
-    // attr.unwrap().clone()
-}
-
-fn call_magic_call(zelf: PyObjectRef, args: PyFuncArgs, vm: &VirtualMachine) -> PyResult {
-    let magic = get_class_magic(&zelf, "__call__");
-    let magic = vm.call_if_get_descriptor(magic, zelf.clone())?;
-    args.insert(zelf);
-    vm.invoke(&magic, args)
-}
-
-fn call_magic_descr_get(
-    vm: &VirtualMachine,
-    zelf: PyObjectRef,
-    obj: Option<PyObjectRef>,
-    cls: OptionalArg<PyObjectRef>,
-) -> PyResult {
-    let magic = get_class_magic(&zelf, "__get__");
-    vm.invoke(
-        &magic,
-        vec![
-            zelf,
-            vm.unwrap_or_none(obj),
-            vm.unwrap_or_none(cls.into_option()),
-        ],
-    )
-}
-
-pub type PyDescrGetFunc = Box<
-    dyn Fn(&VirtualMachine, PyObjectRef, Option<PyObjectRef>, OptionalArg<PyObjectRef>) -> PyResult
-        + Send
-        + Sync,
->;
-
 #[pyimpl]
 pub trait SlotDescriptor: PyValue {
     #[pyslot]
     fn descr_get(
-        vm: &VirtualMachine,
         zelf: PyObjectRef,
         obj: Option<PyObjectRef>,
-        cls: OptionalArg<PyObjectRef>,
+        cls: Option<PyObjectRef>,
+        vm: &VirtualMachine,
     ) -> PyResult;
 
     #[pymethod(magic)]
@@ -163,7 +142,7 @@ pub trait SlotDescriptor: PyValue {
         cls: OptionalArg<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult {
-        Self::descr_get(vm, zelf, Some(obj), cls)
+        Self::descr_get(zelf, Some(obj), cls.into_option(), vm)
     }
 
     fn _zelf(zelf: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
@@ -204,14 +183,11 @@ pub trait SlotDescriptor: PyValue {
         }
     }
 
-    fn _cls_is<T>(cls: &OptionalArg<PyObjectRef>, other: &T) -> bool
+    fn _cls_is<T>(cls: &Option<PyObjectRef>, other: &T) -> bool
     where
         T: IdProtocol,
     {
-        match cls {
-            OptionalArg::Present(cls) => cls.is(other),
-            OptionalArg::Missing => false,
-        }
+        cls.as_ref().map_or(false, |cls| cls.is(other))
     }
 }
 
diff --git a/vm/src/vm.rs b/vm/src/vm.rs
index b84b06555..bcf2157fe 100644
--- a/vm/src/vm.rs
+++ b/vm/src/vm.rs
@@ -23,7 +23,7 @@ use crate::common::{cell::PyMutex, hash::HashSecret, rc::PyRc};
 use crate::exceptions::{self, PyBaseException, PyBaseExceptionRef};
 use crate::frame::{ExecutionResult, Frame, FrameRef};
 use crate::frozen;
-use crate::function::{OptionalArg, PyFuncArgs};
+use crate::function::PyFuncArgs;
 use crate::import;
 use crate::obj::objbool;
 use crate::obj::objcode::{PyCode, PyCodeRef};
@@ -844,7 +844,7 @@ impl VirtualMachine {
         descr
             .class()
             .first_in_mro(|cls| cls.slots.descr_get.load())
-            .map(|descr_get| descr_get(self, descr, obj, OptionalArg::from_option(cls)))
+            .map(|descr_get| descr_get(descr, obj, cls, self))
     }
 
     pub fn call_get_descriptor(&self, descr: PyObjectRef, obj: PyObjectRef) -> Option<PyResult> {
@@ -882,21 +882,19 @@ impl VirtualMachine {
 
     fn _invoke(&self, callable: &PyObjectRef, args: PyFuncArgs) -> PyResult {
         vm_trace!("Invoke: {:?} {:?}", callable, args);
-        let invoked = callable.class().first_in_mro(|cls| {
-            cls.slots.call.load().map(|slot_call| {
+        let slot_call = callable.class().first_in_mro(|cls| cls.slots.call.load());
+        match slot_call {
+            Some(slot_call) => {
                 self.trace_event(TraceEvent::Call)?;
-                let args = args.insert(callable.clone());
-                let result = slot_call(self, args);
+                let result = slot_call(callable.clone(), args, self);
                 self.trace_event(TraceEvent::Return)?;
                 result
-            })
-        });
-        invoked.unwrap_or_else(|| {
-            Err(self.new_type_error(format!(
+            }
+            None => Err(self.new_type_error(format!(
                 "'{}' object is not callable",
                 callable.lease_class().name
-            )))
-        })
+            ))),
+        }
     }
 
     #[inline]