diff --git a/src/mcp/client/sse.py b/src/mcp/client/sse.py
index 2013e4199..3172e5feb 100644
--- a/src/mcp/client/sse.py
+++ b/src/mcp/client/sse.py
@@ -98,6 +98,24 @@ async def sse_reader(
                                             message = types.JSONRPCMessage.model_validate_json(  # noqa: E501
                                                 sse.data
                                             )
+                                            
+                                            # Normalize ID to int 
+                                            # if it's a numeric string.
+                                            if isinstance(  # noqa: E501
+                                                    message.root, 
+                                                    types.JSONRPCResponse
+                                                ):
+                                                msg_id = message.root.id
+                                                if (isinstance(msg_id, str) and 
+                                                    msg_id.isdigit()):
+                                                    message.root.id = int(msg_id)
+                                                elif not isinstance(msg_id, int):
+                                                    logger.warning(
+                                                        "Ignored message with "
+                                                        f"invalid ID: {msg_id!r}"
+                                                    )
+                                                    continue
+                                            
                                             logger.debug(
                                                 f"Received server message: {message}"
                                             )