diff --git a/Makefile b/Makefile
index 57b7f54..50eb1a8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,6 @@
 .PHONY: test
 test:
 	pytest
-
-.PHONY: doctest
-doctest:
 	python -m doctest docs/reference.md
 
 .PHONY: coverage
diff --git a/docs/reference.md b/docs/reference.md
index 0911240..24a8285 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -213,9 +213,9 @@ Same as `FilterKeys` but for `v` in `(k, v)` pairs
 
 # case-insensitive
 >>> ['hello foo', 'world', 'awesome FOo'] | Grep('foo', i=True) | Pipe(list)
-['hello foo', 'awesome foo']
+['hello foo', 'awesome FOo']
 >>> ['hello foo', 'world', 'awesome FOo'] | Grep('Foo', i=True) | Pipe(list)
-['hello foo', 'awesome foo']
+['hello foo', 'awesome FOo']
 
 # invert match
 >>> ['hello foo', 'world', 'awesome FOo'] | Grep('foo', v=True) | Pipe(list)
diff --git a/pipe21.py b/pipe21.py
index 2caf65e..b43a990 100644
--- a/pipe21.py
+++ b/pipe21.py
@@ -29,7 +29,7 @@ class ValueBy      (B): __ror__ = lambda self, it: it | Map(lambda x: (x, self.f
 class Append       (B): __ror__ = lambda self, it: it | Map(lambda x: (*x, self.f(x)))
 class Keys         (B): __ror__ = lambda self, it: it | Map(lambda kv: kv[0])
 class Values       (B): __ror__ = lambda self, it: it | Map(lambda kv: kv[1])
-class Grep         (B): __ror__ = lambda self, it: it | MapSwitch([(lambda x: self.kw.setdefault('i', False), str.lower)]) | (FilterFalse if self.kw.get('v', False) else Filter)(lambda x: re.search(self.f.lower() if self.kw['i'] else self.f, x))
+class Grep         (B): __ror__ = lambda self, it: it | (FilterFalse if self.kw.get('v', False) else Filter)(re.compile(self.f, flags=re.I if self.kw.get('i', False) else 0).search)
 class IterLines    (B): __ror__ = lambda self, p: p | Pipe(open) | Pipe(lambda t: t | Map(str.strip) if self.kw.get('strip', True) else t)
 class Count        (B): __ror__ = lambda self, it: sum(1 for _ in it)
 class Slice        (B): __ror__ = lambda self, it: itertools.islice(it, self.f, *self.args)
diff --git a/tests/pipe_test.py b/tests/pipe_test.py
index a087fcc..e9b1494 100644
--- a/tests/pipe_test.py
+++ b/tests/pipe_test.py
@@ -190,8 +190,8 @@ def test_grep_v(it, grep, expected):
 @pytest.mark.parametrize(
     ('it', 'grep', 'v', 'i', 'expected'), [
         (['hello foo', 'world', 'awesome FOo'], 'foo', False, False, ['hello foo']),
-        (['hello foo', 'world', 'awesome FOo'], 'foo', False, True, ['hello foo', 'awesome foo']),
-        (['hello foo', 'world', 'awesome FOo'], 'Foo', False, True, ['hello foo', 'awesome foo']),
+        (['hello foo', 'world', 'awesome FOo'], 'foo', False, True, ['hello foo', 'awesome FOo']),
+        (['hello foo', 'world', 'awesome FOo'], 'Foo', False, True, ['hello foo', 'awesome FOo']),
         (['hello foo', 'world', 'awesome FOo'], 'foo', True, False, ['world', 'awesome FOo']),
         (['hello foo', 'world', 'awesome FOo'], 'foo', True, True, ['world']),
         (['hello foo', 'world', 'awesome FOo'], 'Foo', True, True, ['world']),