<<<
--- /scikit-learn__scikit-learn/sklearn/preprocessing/label.py
+++ /scikit-learn__scikit-learn/sklearn/preprocessing/label.py
@@ -127,6 +127,8 @@
         if len(np.intersect1d(classes, self.classes_)) < len(classes):
             diff = np.setdiff1d(classes, self.classes_)
             raise ValueError("y contains previously unseen labels: %s" % str(diff))
+        if len(y) == 0:
+            return np.empty_like(self.classes_, dtype=self.classes_.dtype)
         return np.searchsorted(self.classes_, y)
 
     def inverse_transform(self, y):
>>>