diff --git a/flair/training_utils.py b/flair/training_utils.py
index 915df609a8..2ac1fe378e 100644
--- a/flair/training_utils.py
+++ b/flair/training_utils.py
@@ -28,11 +28,22 @@ def __init__(
         self,
         main_score: float,
         detailed_results: str,
+        scores: dict,
         classification_report: Optional[dict] = None,
-        scores: Optional[dict] = None,
     ) -> None:
-        classification_report = classification_report if classification_report is not None else {}
-        assert scores is not None and "loss" in scores, "No loss provided."
+        """Initialize Result object for model evaluation.
+
+        Args:
+            main_score: The primary evaluation metric
+            detailed_results: Detailed evaluation results as string
+            scores: Dictionary containing evaluation metrics including 'loss'
+            classification_report: Optional classification report dictionary
+
+        Raises:
+            ValueError: If scores does not contain 'loss' key
+        """
+        if "loss" not in scores:
+            raise ValueError("scores parameter must contain 'loss' key")
 
         self.main_score: float = main_score
         self.scores = scores
@@ -40,7 +51,7 @@ def __init__(
         self.classification_report = classification_report if classification_report is not None else {}
 
     @property
-    def loss(self):
+    def loss(self) -> float:
         return self.scores["loss"]
 
     def __str__(self) -> str: