diff --git a/src/crewai/flow/flow.py b/src/crewai/flow/flow.py
index 85e80c1bd..16f1cf9f0 100644
--- a/src/crewai/flow/flow.py
+++ b/src/crewai/flow/flow.py
@@ -11,6 +11,7 @@ from typing import (
     Type,
     TypeVar,
     Union,
+    cast,
 )
 
 from pydantic import BaseModel, ValidationError
@@ -216,10 +217,18 @@ class Flow(Generic[T], metaclass=FlowMeta):
         if isinstance(self._state, BaseModel):
             # Structured state management
             try:
-                # Create a new instance with updated values to ensure validation
-                self._state = self._state.__class__(
-                    **{**self._state.model_dump(), **inputs}
+                M = self._state.__class__
+
+                # Dynamically create a new model class with 'extra' set to 'forbid'
+                class ModelWithExtraForbid(M):
+                    model_config = M.model_config.copy()
+                    model_config["extra"] = "forbid"
+
+                # Create a new instance using the combined state and inputs
+                self._state = cast(
+                    T, ModelWithExtraForbid(**{**self._state.model_dump(), **inputs})
                 )
+
             except ValidationError as e:
                 raise ValueError(f"Invalid inputs for structured state: {e}") from e
         elif isinstance(self._state, dict):