diff --git a/commlib/msg.py b/commlib/msg.py
index 54b7ca4..3799c89 100644
--- a/commlib/msg.py
+++ b/commlib/msg.py
@@ -3,7 +3,7 @@
 from typing import Any, Dict, List, Union
 from uuid import UUID
 
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 
 from commlib.utils import gen_timestamp
 
@@ -22,7 +22,7 @@ class MessageHeader(BaseModel):
     msg_id: Union[int, str, UUID] = -1
     node_id: Union[int, str, UUID] = ""
     agent: str = "commlib-py"
-    timestamp: int = gen_timestamp()
+    timestamp: int = Field(default_factory=lambda: gen_timestamp())
     properties: Dict[str, Any] = {}
 
 
diff --git a/commlib/utils.py b/commlib/utils.py
index 0656895..806ee8e 100644
--- a/commlib/utils.py
+++ b/commlib/utils.py
@@ -30,7 +30,7 @@ def gen_timestamp() -> int:
         int: Timestamp in integer representation. User `str()` to
             transform to string.
     """
-    return int(1.0 * (time.time() + 0.5) * 1000)
+    return int(1.0 * (time.time_ns() + 0.5) * 1000)
 
 
 def gen_random_id() -> str:
diff --git a/examples/simple_pubsub/publisher.py b/examples/simple_pubsub/publisher.py
index 83cd686..9057e67 100755
--- a/examples/simple_pubsub/publisher.py
+++ b/examples/simple_pubsub/publisher.py
@@ -3,12 +3,14 @@
 import sys
 import time
 
+from pydantic import Field
+
 from commlib.msg import MessageHeader, PubSubMessage
 from commlib.node import Node
 
 
 class SonarMessage(PubSubMessage):
-    header: MessageHeader = MessageHeader()
+    header: MessageHeader = Field(default_factory=lambda: MessageHeader())
     range: float = -1
     hfov: float = 30.6
     vfov: float = 14.2