diff --git a/vm/src/pyobject.rs b/vm/src/pyobject.rs
index 02c563aaf2..b196d9311c 100644
--- a/vm/src/pyobject.rs
+++ b/vm/src/pyobject.rs
@@ -314,6 +314,10 @@ impl PyContext {
     }
 
     pub fn new_base_object(&self, class: PyTypeRef, dict: Option<PyDictRef>) -> PyObjectRef {
+        debug_assert_eq!(
+            class.slots.flags.contains(PyTypeFlags::HAS_DICT),
+            dict.is_some()
+        );
         PyObject::new(object::PyBaseObject, class, dict)
     }
 }