diff --git a/nac3artiq/demo/class_instantiation_test.py b/nac3artiq/demo/class_instantiation_test.py
new file mode 100644
index 0000000..7d8608a
--- /dev/null
+++ b/nac3artiq/demo/class_instantiation_test.py
@@ -0,0 +1,26 @@
+from min_artiq import *
+from numpy import int32, ceil
+
+
+@nac3
+class Foo:
+    attr: KernelInvariant[int32]
+        
+@nac3
+class Bar:
+    core: KernelInvariant[Core]
+    attr2: KernelInvariant[int32]
+
+    def __init__(self):
+        self.core = Core()
+        self.attr2 = 4
+
+    @kernel
+    def run(self):
+        self.core.reset()
+        a: Foo = Foo()
+        
+
+
+if __name__ == "__main__":
+    Bar().run()
\ No newline at end of file
diff --git a/nac3artiq/src/symbol_resolver.rs b/nac3artiq/src/symbol_resolver.rs
index 0b9ede9..8d271da 100644
--- a/nac3artiq/src/symbol_resolver.rs
+++ b/nac3artiq/src/symbol_resolver.rs
@@ -300,6 +300,14 @@ impl InnerResolver {
         let ty_id: u64 = self.helper.id_fn.call1(py, (pyty,))?.extract(py)?;
         let ty_ty_id: u64 =
             self.helper.id_fn.call1(py, (self.helper.type_fn.call1(py, (pyty,))?,))?.extract(py)?;
+        let py_obj_id: u64 = self.helper.id_fn.call1(py, (pyty,))?.extract(py)?;
+        let get_def_id = || {
+            self.pyid_to_def
+                .read()
+                .get(&ty_id)
+                .copied()
+                .or_else(|| self.pyid_to_def.read().get(&py_obj_id).copied())
+        };
 
         if ty_id == self.primitive_ids.int || ty_id == self.primitive_ids.int32 {
             Ok(Ok((primitives.int32, true)))
@@ -333,7 +341,7 @@ impl InnerResolver {
             Ok(Ok((primitives.option, false)))
         } else if ty_id == self.primitive_ids.none {
             unreachable!("none cannot be typeid")
-        } else if let Some(def_id) = self.pyid_to_def.read().get(&ty_id).copied() {
+        } else if let Some(def_id) = get_def_id() {
             let def = defs[def_id.0].read();
             let TopLevelDef::Class { object_id, type_vars, fields, methods, .. } = &*def else {
                 // only object is supported, functions are not supported
@@ -599,12 +607,15 @@ impl InnerResolver {
         let pyid_to_def = self.pyid_to_def.read();
         let constructor_ty = pyid_to_def.get(&py_obj_id).and_then(|def_id| {
             defs.iter().find_map(|def| {
-                if let TopLevelDef::Class { object_id, methods, constructor, .. } = &*def.read() {
-                    if object_id == def_id
-                        && constructor.is_some()
-                        && methods.iter().any(|(s, _, _)| s == &"__init__".into())
+                if let Some(rear_guard) = def.try_read() {
+                    if let TopLevelDef::Class { object_id, methods, constructor, .. } = &*rear_guard
                     {
-                        return *constructor;
+                        if object_id == def_id
+                            && constructor.is_some()
+                            && methods.iter().any(|(s, _, _)| s == &"__init__".into())
+                        {
+                            return *constructor;
+                        }
                     }
                 }
                 None
@@ -625,6 +636,7 @@ impl InnerResolver {
                     self.primitive_ids.generic_alias.1,
                 ]
                 .contains(&self.helper.id_fn.call1(py, (ty.clone(),))?.extract::<u64>(py)?)
+                    || self.pyid_to_def.read().contains_key(&py_obj_id)
                 {
                     obj
                 } else {