diff --git a/src/claude_code_sdk/_internal/client.py b/src/claude_code_sdk/_internal/client.py
index 9e8ceace..1057ae6e 100644
--- a/src/claude_code_sdk/_internal/client.py
+++ b/src/claude_code_sdk/_internal/client.py
@@ -86,13 +86,13 @@ def _parse_message(self, data: dict[str, Any]) -> Message | None:
                 # Map total_cost to total_cost_usd for consistency
                 return ResultMessage(
                     subtype=data["subtype"],
-                    cost_usd=data["cost_usd"],
+                    # cost_usd=data["cost_usd"],
                     duration_ms=data["duration_ms"],
                     duration_api_ms=data["duration_api_ms"],
                     is_error=data["is_error"],
                     num_turns=data["num_turns"],
                     session_id=data["session_id"],
-                    total_cost_usd=data["total_cost"],
+                    # total_cost_usd=data["total_cost"],
                     usage=data.get("usage"),
                     result=data.get("result"),
                 )
diff --git a/src/claude_code_sdk/types.py b/src/claude_code_sdk/types.py
index a80510bc..a5dcdae8 100644
--- a/src/claude_code_sdk/types.py
+++ b/src/claude_code_sdk/types.py
@@ -75,13 +75,13 @@ class ResultMessage:
     """Result message with cost and usage information."""
 
     subtype: str
-    cost_usd: float
     duration_ms: int
     duration_api_ms: int
     is_error: bool
     num_turns: int
     session_id: str
-    total_cost_usd: float
+    cost_usd: float | None = None
+    total_cost_usd: float | None = None
     usage: dict[str, Any] | None = None
     result: str | None = None