diff --git a/jedi/common.py b/jedi/common.py
index 5c42e0b0..e188f781 100644
--- a/jedi/common.py
+++ b/jedi/common.py
@@ -29,10 +29,11 @@ class PushBackIterator(object):
 
 
 class NoErrorTokenizer(object):
-    def __init__(self, readline, line_offset=0):
+    def __init__(self, readline, line_offset=0, stop_on_scope=False):
         self.readline = readline
         self.gen = PushBackIterator(tokenize.generate_tokens(readline))
         self.line_offset = line_offset
+        self.stop_on_scope = stop_on_scope
 
     def push_last_back(self):
         self.gen.push_back(self.current)
@@ -61,7 +62,13 @@ class NoErrorTokenizer(object):
             self.gen = PushBackIterator(tokenize.generate_tokens(
                                                                 self.readline))
             self.current = self.next()
+
         c = list(self.current)
+
+        # stop if a new class or definition is started at position zero.
+        if self.stop_on_scope and c[1] in ['def', 'class'] and c[2][1] == 0:
+            raise StopIteration()
+
         c[2] = self.line_offset + c[2][0], c[2][1]
         return c
 
diff --git a/jedi/parsing.py b/jedi/parsing.py
index e5c32754..fe656628 100644
--- a/jedi/parsing.py
+++ b/jedi/parsing.py
@@ -244,6 +244,8 @@ class Module(Scope):
         self._name = None
         self.used_names = {}
         self.temp_used_names = []
+        # this may be changed depending on fast_parser
+        self.line_offset = 0
 
     def add_global(self, name):
         """
@@ -1137,10 +1139,10 @@ class PyFuzzyParser(object):
     :param user_position: The line/column, the user is currently on.
     :type user_position: tuple(int, int)
     :param no_docstr: If True, a string at the beginning is not a docstr.
-    :param tokenize_gen: A prepared tokenize generator -> for fast_parser
+    :param stop_on_scope: Stop if a scope appears -> for fast_parser
     """
     def __init__(self, code, module_path=None, user_position=None,
-                            no_docstr=False, line_offset=0, tokenize_gen=None):
+                        no_docstr=False, line_offset=0, stop_on_scope=None):
         self.user_position = user_position
         self.user_scope = None
         self.user_stmt = None
@@ -1157,12 +1159,10 @@ class PyFuzzyParser(object):
         # any errors of tokenize and just parse ahead.
         self._line_offset = line_offset
 
-        if tokenize_gen is None:
-            code = code + '\n'  # end with \n, because the parser needs it
-            buf = StringIO(code)
-            self.gen = common.NoErrorTokenizer(buf.readline, line_offset)
-        else:
-            self.gen = tokenize_gen
+        code = code + '\n'  # end with \n, because the parser needs it
+        buf = StringIO(code)
+        self.gen = common.NoErrorTokenizer(buf.readline, line_offset,
+                                                            stop_on_scope)
         self.parse()
 
     def __repr__(self):