diff --git a/jedi/parser/fast.py b/jedi/parser/fast.py
index 41f3a525..672b7202 100644
--- a/jedi/parser/fast.py
+++ b/jedi/parser/fast.py
@@ -489,7 +489,7 @@ class FastTokenizer(object):
             return current
 
         if value in ('def', 'class') and self._parentheses_level \
-                and re.match('\n[ \t]*\Z', prefix):
+                and re.search(r'\n[ \t]*\Z', prefix):
             # Account for the fact that an open parentheses before a function
             # will reset the parentheses counter, but new lines before will
             # still be ignored. So check the prefix.
diff --git a/test/test_parser/test_fast_parser.py b/test/test_parser/test_fast_parser.py
index 7a524fab..7d0a5289 100644
--- a/test/test_parser/test_fast_parser.py
+++ b/test/test_parser/test_fast_parser.py
@@ -324,10 +324,10 @@ def test_wrong_indentation():
 
 def test_open_parentheses():
     func = 'def func():\n a'
-    p = FastParser(load_grammar(), 'isinstance(\n' + func)
+    p = FastParser(load_grammar(), 'isinstance(\n\n' + func)
     # As you can see, the isinstance call cannot be seen anymore after
     # get_code, because it isn't valid code.
-    assert p.module.get_code() == '\n' + func
+    assert p.module.get_code() == '\n\n' + func
     assert p.number_of_splits == 2
     assert p.number_parsers_used == 2
     cache.save_parser(None, None, p, pickling=False)