diff --git a/lib/crewai/src/crewai/utilities/config.py b/lib/crewai/src/crewai/utilities/config.py
index 95a542c5e..d558d6dd0 100644
--- a/lib/crewai/src/crewai/utilities/config.py
+++ b/lib/crewai/src/crewai/utilities/config.py
@@ -14,7 +14,16 @@ def process_config(
 
     Returns:
         The updated values dictionary.
+
+    Raises:
+        ValueError: If values is not a dictionary (e.g. when an invalid type
+            is passed for a field that expects a Pydantic model).
     """
+    if not isinstance(values, dict):
+        raise ValueError(
+            f"{model_class.__name__} expected a mapping/dictionary, "
+            f"got {type(values).__name__}"
+        )
     config = values.get("config", {})
     if not config:
         return values
diff --git a/lib/crewai/tests/test_task.py b/lib/crewai/tests/test_task.py
index 9a0010d89..140098e82 100644
--- a/lib/crewai/tests/test_task.py
+++ b/lib/crewai/tests/test_task.py
@@ -1748,3 +1748,50 @@ def test_async_execution_fails():
       with pytest.raises(RuntimeError, match="boom!"):
         execution = task.execute_async(agent=researcher)
         execution.result()
+
+
+def test_task_with_invalid_agent_string_raises_validation_error():
+    with pytest.raises(ValidationError) as exc_info:
+        Task(
+            description="Test task",
+            expected_output="Test output",
+            agent="not_an_agent",
+        )
+    assert "BaseAgent expected a mapping/dictionary, got str" in str(exc_info.value)
+
+
+def test_task_with_invalid_agent_int_raises_validation_error():
+    with pytest.raises(ValidationError) as exc_info:
+        Task(
+            description="Test task",
+            expected_output="Test output",
+            agent=123,
+        )
+    assert "BaseAgent expected a mapping/dictionary, got int" in str(exc_info.value)
+
+
+def test_task_with_invalid_agent_list_raises_validation_error():
+    with pytest.raises(ValidationError) as exc_info:
+        Task(
+            description="Test task",
+            expected_output="Test output",
+            agent=[1, 2, 3],
+        )
+    assert "BaseAgent expected a mapping/dictionary, got list" in str(exc_info.value)
+
+
+def test_task_with_none_agent_is_valid():
+    task = Task(
+        description="Test task",
+        expected_output="Test output",
+        agent=None,
+    )
+    assert task.agent is None
+
+
+def test_task_without_agent_is_valid():
+    task = Task(
+        description="Test task",
+        expected_output="Test output",
+    )
+    assert task.agent is None