diff --git a/jedi/api.py b/jedi/api.py
index a91e3e76..7b325933 100644
--- a/jedi/api.py
+++ b/jedi/api.py
@@ -56,7 +56,7 @@ class Script(object):
     :type source_encoding: str
     """
     def __init__(self, source, line, column, source_path,
-                 source_encoding='utf-8', fast=True):
+                 source_encoding='utf-8', fast=None):
         api_classes._clear_caches()
         debug.reset_time()
         self.source = modules.source_to_unicode(source, source_encoding)
diff --git a/jedi/modules.py b/jedi/modules.py
index 4a66d477..462e6989 100644
--- a/jedi/modules.py
+++ b/jedi/modules.py
@@ -91,9 +91,13 @@ class ModuleWithCursor(Module):
     :param path: The module path of the file or None.
     :param position: The position, the user is currently in. Only important \
     for the main file.
+    :param fast: Use `fast_parser.FastParser` or not.  If None, respect
+                 `settings.fast_parser`.
     """
-    def __init__(self, path, source, position, fast=True):
+    def __init__(self, path, source, position, fast=None):
         super(ModuleWithCursor, self).__init__(path, source)
+        if fast is None:
+            fast = settings.fast_parser
         self._parserclass = fast_parser.FastParser if fast else \
                             parsing.Parser
         self.position = position