diff --git a/realtime/_async/client.py b/realtime/_async/client.py
index fda8487..c099e9d 100644
--- a/realtime/_async/client.py
+++ b/realtime/_async/client.py
@@ -2,7 +2,10 @@
 import json
 import logging
 import re
+from base64 import b64decode
+from datetime import datetime
 from functools import wraps
+from math import floor
 from typing import Any, Callable, Dict, List, Optional
 
 import websockets
@@ -256,6 +259,30 @@ async def set_auth(self, token: Optional[str]) -> None:
         Returns:
             None
         """
+        # No empty string tokens.
+        if isinstance(token, str) and len(token.strip()) == 0:
+            raise ValueError("Provide a valid jwt token")
+
+        if token:
+            parsed = None
+            try:
+                payload = token.split(".")[1] + "=="
+                parsed = json.loads(b64decode(payload).decode("utf-8"))
+            except Exception:
+                raise ValueError("InvalidJWTToken")
+
+            if parsed:
+                # Handle expired token if any.
+                if "exp" in parsed:
+                    now = floor(datetime.now().timestamp())
+                    valid = now - parsed["exp"] < 0
+                    if not valid:
+                        raise ValueError(
+                            f"InvalidJWTToken: Invalid value for JWT claim 'exp' with value { parsed['exp'] }"
+                        )
+                else:
+                    raise ValueError("InvalidJWTToken: expected claim 'exp'")
+
         self.access_token = token
 
         for _, channel in self.channels.items():
diff --git a/tests/test_connection.py b/tests/test_connection.py
index fd510c9..1ee658a 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -49,8 +49,8 @@ async def access_token() -> str:
 async def test_set_auth(socket: AsyncRealtimeClient):
     await socket.connect()
 
-    await socket.set_auth("jwt")
-    assert socket.access_token == "jwt"
+    with pytest.raises(ValueError):
+        await socket.set_auth("jwt")  # Invalid JWT.
 
     await socket.close()