diff --git a/jedi/parser/python/__init__.py b/jedi/parser/python/__init__.py
index 9b7ca75f..3f86dfb5 100644
--- a/jedi/parser/python/__init__.py
+++ b/jedi/parser/python/__init__.py
@@ -3,6 +3,7 @@ Parsers for Python
 """
 import os
 
+from jedi import settings
 from jedi._compatibility import FileNotFoundError
 from jedi.parser.pgen2.pgen import generate_grammar
 from jedi.parser.python.parser import Parser, _remove_last_newline
@@ -86,7 +87,7 @@ def parse(code=None, path=None, grammar=None, error_recovery=True,
         with open(path, 'rb') as f:
             code = source_to_unicode(f.read())
 
-    if diff_cache:
+    if diff_cache and settings.fast_parser:
         try:
             module_cache_item = parser_cache[path]
         except KeyError:
diff --git a/jedi/parser/python/diff.py b/jedi/parser/python/diff.py
index 3da9809d..3d4715eb 100644
--- a/jedi/parser/python/diff.py
+++ b/jedi/parser/python/diff.py
@@ -9,35 +9,14 @@ import re
 import difflib
 from collections import namedtuple
 
-from jedi._compatibility import use_metaclass
-from jedi import settings
 from jedi.common import splitlines
 from jedi.parser.python.parser import Parser, _remove_last_newline
 from jedi.parser.python.tree import EndMarker
-from jedi.parser.cache import parser_cache
 from jedi import debug
 from jedi.parser.tokenize import (generate_tokens, NEWLINE, TokenInfo,
                                   ENDMARKER, INDENT, DEDENT)
 
 
-class CachedFastParser(type):
-    """ This is a metaclass for caching `FastParser`. """
-    def __call__(self, grammar, source, module_path=None):
-        pi = parser_cache.get(module_path, None)
-        if pi is None or not settings.fast_parser:
-            return Parser(grammar, source, module_path)
-
-        parser = pi.parser
-        d = DiffParser(parser)
-        new_lines = splitlines(source, keepends=True)
-        parser.module = parser._parsed = d.update(new_lines)
-        return parser
-
-
-class FastParser(use_metaclass(CachedFastParser)):
-    pass
-
-
 def _get_last_line(node_or_leaf):
     last_leaf = node_or_leaf.get_last_leaf()
     if _ends_with_newline(last_leaf):