diff --git a/betterproto-extras/src/descriptor_pool.rs b/betterproto-extras/src/descriptor_pool.rs
index 7ffee0e..90b0e98 100644
--- a/betterproto-extras/src/descriptor_pool.rs
+++ b/betterproto-extras/src/descriptor_pool.rs
@@ -4,7 +4,8 @@ use crate::{
 };
 use prost_reflect::{
     prost_types::{
-        field_descriptor_proto::{Type, Label}, DescriptorProto, FieldDescriptorProto, FileDescriptorProto,
+        field_descriptor_proto::{Label, Type},
+        DescriptorProto, FieldDescriptorProto, FileDescriptorProto, OneofDescriptorProto,
     },
     DescriptorPool, MessageDescriptor,
 };
@@ -69,6 +70,27 @@ fn create_cached_descriptor_in_pool<'py>(
                 field.set_label(Label::Repeated);
             }
 
+            if let Some(grp) = meta.oneof_group(field_name)? {
+                let oneof_index = message
+                    .oneof_decl
+                    .iter()
+                    .enumerate()
+                    .filter(|x| x.1.name() == grp)
+                    .map(|x| x.0)
+                    .last();
+
+                match oneof_index {
+                    Some(i) => field.oneof_index = Some(i as i32),
+                    None => {
+                        message.oneof_decl.push(OneofDescriptorProto {
+                            name: Some(grp),
+                            ..Default::default()
+                        });
+                        field.oneof_index = Some((message.oneof_decl.len() - 1) as i32)
+                    }
+                }
+            }
+
             field
         });
     }
diff --git a/betterproto-extras/src/merging.rs b/betterproto-extras/src/merging.rs
index 6fe118f..88d12eb 100644
--- a/betterproto-extras/src/merging.rs
+++ b/betterproto-extras/src/merging.rs
@@ -9,11 +9,13 @@ pub fn merge_msg_into_pyobj(obj: &PyAny, msg: &DynamicMessage) -> Result<()> {
     for field in msg.descriptor().fields() {
         let field_name = field.name();
         let proto_meta = obj.get_proto_meta()?;
-        if let Some(field_value) = msg.get_field_by_name(field_name) {
-            obj.setattr(
-                field_name,
-                map_field_value(field_name, &field_value, proto_meta)?,
-            )?;
+        if msg.has_field_by_name(field_name) {
+            if let Some(field_value) = msg.get_field_by_name(field_name) {
+                obj.setattr(
+                    field_name,
+                    map_field_value(field_name, &field_value, proto_meta)?,
+                )?;
+            }
         }
     }
     Ok(())
diff --git a/betterproto-extras/src/py_any_extras.rs b/betterproto-extras/src/py_any_extras.rs
index f42611a..1c7e9cb 100644
--- a/betterproto-extras/src/py_any_extras.rs
+++ b/betterproto-extras/src/py_any_extras.rs
@@ -1,14 +1,15 @@
 use crate::error::Result;
 use pyo3::PyAny;
 
-pub trait PyAnyExtras<'py> {
+pub trait PyAnyExtras {
     fn qualified_class_name(&self) -> Result<String>;
-    fn get_proto_meta(&self) -> Result<&'py PyAny>;
-    fn create_instance(&self, field_name: &str) -> Result<&'py PyAny>;
+    fn get_proto_meta(&self) -> Result<&PyAny>;
+    fn create_instance(&self, field_name: &str) -> Result<&PyAny>;
     fn is_list_field(&self, field_name: &str) -> Result<bool>;
+    fn oneof_group(&self, field_name: &str) -> Result<Option<String>>;
 }
 
-impl<'py> PyAnyExtras<'py> for &'py PyAny {
+impl PyAnyExtras for PyAny {
     fn qualified_class_name(&self) -> Result<String> {
         let class = self.getattr("__class__")?;
         let module = class.getattr("__module__")?;
@@ -16,11 +17,11 @@ impl<'py> PyAnyExtras<'py> for &'py PyAny {
         Ok(format!("{module}.{name}"))
     }
 
-    fn get_proto_meta(&self) -> Result<&'py PyAny> {
+    fn get_proto_meta(&self) -> Result<&PyAny> {
         Ok(self.getattr("_betterproto")?)
     }
 
-    fn create_instance(&self, field_name: &str) -> Result<&'py PyAny> {
+    fn create_instance(&self, field_name: &str) -> Result<&PyAny> {
         let res = self
             .getattr("cls_by_field")?
             .get_item(field_name)?
@@ -34,4 +35,12 @@ impl<'py> PyAnyExtras<'py> for &'py PyAny {
         let name = cls.getattr("__name__")?;
         Ok(module.to_string() == "builtins" && name.to_string() == "list")
     }
+
+    fn oneof_group(&self, field_name: &str) -> Result<Option<String>> {
+        let opt = self
+            .getattr("oneof_group_by_field")?
+            .call_method1("get", (field_name,))?
+            .extract()?;
+        Ok(opt)
+    }
 }
diff --git a/example.py b/example.py
index ca69ed8..2f1048a 100644
--- a/example.py
+++ b/example.py
@@ -5,17 +5,20 @@ import betterproto
 from dataclasses import dataclass
 from typing import List
 
-@dataclass
+@dataclass(repr=False)
 class Baz(betterproto.Message):
-    a: str = betterproto.string_field(1)
+    a: float = betterproto.float_field(1, group = "x")
+    b: int = betterproto.int64_field(2, group = "x")
+    c: float = betterproto.float_field(3, group = "y")
+    d: int = betterproto.int64_field(4, group = "y")
 
-@dataclass
+@dataclass(repr=False)
 class Foo(betterproto.Message):
     x: int = betterproto.int32_field(1)
     y: float = betterproto.double_field(2)
     z: List[Baz] = betterproto.message_field(3)
 
-@dataclass
+@dataclass(repr=False)
 class Bar(betterproto.Message):
     foo1: Foo = betterproto.message_field(1)
     foo2: Foo = betterproto.message_field(2)
@@ -25,7 +28,7 @@ class Bar(betterproto.Message):
 buffer = bytes(
     Bar(
         foo1=Foo(1, 2.34),
-        foo2=Foo(3, 4.56, [Baz("Hi"), Baz("There")]),
+        foo2=Foo(3, 4.56, [Baz(a = 1.234), Baz(b = 5), Baz(b = 2, d = 3)]),
         packed=[5, 3, 1]
     )
 )