diff --git a/python/fbprophet/models.py b/python/fbprophet/models.py
index a4ac0a6..38102df 100644
--- a/python/fbprophet/models.py
+++ b/python/fbprophet/models.py
@@ -28,8 +28,12 @@ class IStanBackend(ABC):
         Specify model options as kwargs.
          * newton_fallback [bool]: whether to fallback to Newton if L-BFGS fails
         """
-        if 'newton_fallback' in kwargs:
-            self.newton_fallback = kwargs['newton_fallback']
+        for k, v in kwargs.items():
+            if k == 'newton_fallback':
+                self.newton_fallback = v
+            else:
+                raise ValueError(f'Unknown option {k}')
+
 
     @staticmethod
     @abstractmethod
@@ -291,4 +295,4 @@ class StanBackendEnum(Enum):
         try:
             return StanBackendEnum[name].value
         except KeyError as e:
-            raise ValueError("Unknown stan backend: {}".format(name)) from e
\ No newline at end of file
+            raise ValueError("Unknown stan backend: {}".format(name)) from e