diff --git a/lazy_dataset/database.py b/lazy_dataset/database.py
index c37891d..2acfba9 100644
--- a/lazy_dataset/database.py
+++ b/lazy_dataset/database.py
@@ -81,6 +81,10 @@ def data(self):
         raise NotImplementedError(
             f'Override this property in {self.__class__.__name__}!')
 
+    @property
+    def alias(self):
+        return self.data.setdefault('alias', {})
+
     @property
     def dataset_names(self):
         """
@@ -90,7 +94,7 @@ def dataset_names(self):
         return tuple(
             self.data['datasets'].keys()
         ) + tuple(
-            self.data.get('alias', {}).keys()
+            self.alias.keys()
         )
 
     def get_examples(self, dataset_name):
@@ -107,8 +111,8 @@ def get_examples(self, dataset_name):
 
         """
         try:
-            if dataset_name in self.data.get('alias', []):
-                dataset_names = self.data['alias'][dataset_name]
+            if dataset_name in self.alias:
+                dataset_names = self.alias[dataset_name]
                 examples = {}
                 for name in dataset_names:
                     examples_new = self.data['datasets'][name]
@@ -286,8 +290,18 @@ def __reduce__(self):
     @property
     def data(self):
         if self._data is None:
+            def read_text(path):
+                try:
+                    path = Path(path)
+                except TypeError:
+                    if isinstance(path, dict):
+                        raise TypeError(f'{self.__class__.__qualname__} got a {type(path)} as json_path. Did you mean to use DictDatabase?')
+                    else:
+                        raise
+                return path.expanduser().read_text()
+
             self._data = _merge_database_dicts(*[
-                json.loads(Path(path).expanduser().read_text())
+                json.loads(read_text(path))
                 for path in self._json_path
             ])