diff --git a/scikit_tt/tensor_train.py b/scikit_tt/tensor_train.py
index c9a6783..0373f35 100644
--- a/scikit_tt/tensor_train.py
+++ b/scikit_tt/tensor_train.py
@@ -1323,30 +1323,12 @@ def ortho(self, threshold: float=0, max_rank: Union[int, List[int]]=np.infty) ->
         -------
         TT
            right-orthonormalized representation of self
-
-        Raises
-        ------
-        ValueError
-            if threshold is less than 0
-        ValueError
-            if max_rank is not a positive integer
         """
 
-        if isinstance(threshold, (int, np.int32, np.int64, float, np.float32, np.float64)) and threshold >= 0:
+        # left- and right-orthonormalize self
+        self.ortho_left(threshold=threshold, max_rank=np.infty).ortho_right(threshold=threshold, max_rank=max_rank)
 
-            if (isinstance(max_rank, (int, np.int32, np.int64)) and max_rank > 0) or max_rank == np.infty:
-
-                # left- and right-orthonormalize self
-                self.ortho_left(threshold=threshold, max_rank=np.infty).ortho_right(threshold=threshold,
-                                                                                    max_rank=max_rank)
-
-                return self
-
-            else:
-                raise ValueError('Maximum rank must be a positive integer.')
-
-        else:
-            raise ValueError('Threshold must be greater or equal 0.')
+        return self
 
     def norm(self, p: int=2) -> float:
         """