diff --git a/pydantic/typing.py b/pydantic/typing.py
index 684c6fd02b3..31c8f74ea21 100644
--- a/pydantic/typing.py
+++ b/pydantic/typing.py
@@ -177,6 +177,19 @@ def literal_values(type_: AnyType) -> Tuple[Any, ...]:
         return type_.__values__
 
 
+def all_literal_values(type_: Type[Any]) -> Tuple[Any, ...]:
+    """
+    This method is used to retrieve all Literal values as
+    Literal can be used recursively (see https://www.python.org/dev/peps/pep-0586)
+    e.g. `Literal[Literal[Literal[1, 2, 3], "foo"], 5, None]`
+    """
+    if not is_literal_type(type_):
+        return (type_,)
+
+    values = literal_values(type_)
+    return tuple(x for value in values for x in all_literal_values(value))
+
+
 test_type = NewType('test_type', str)
 
 
diff --git a/pydantic/validators.py b/pydantic/validators.py
index d36e16de7c4..0a45cbab4be 100644
--- a/pydantic/validators.py
+++ b/pydantic/validators.py
@@ -28,11 +28,11 @@
     AnyCallable,
     AnyType,
     ForwardRef,
+    all_literal_values,
     display_as_type,
     get_class,
     is_callable_type,
     is_literal_type,
-    literal_values,
 )
 from .utils import almost_equal_floats, lenient_issubclass, sequence_like
 
@@ -393,18 +393,8 @@ def callable_validator(v: Any) -> AnyCallable:
     raise errors.CallableError(value=v)
 
 
-def flatten_literal(s: Any) -> List[Any]:
-    if is_literal_type(s):
-        s = list(literal_values(s))
-    if s == []:
-        return s
-    if is_literal_type(s[0]):
-        return flatten_literal(s[0]) + flatten_literal(s[1:])
-    return s[:1] + flatten_literal(s[1:])
-
-
 def make_literal_validator(type_: Any) -> Callable[[Any], Any]:
-    permitted_choices: Tuple[Any, ...] = tuple(flatten_literal(type_))
+    permitted_choices: Tuple[Any, ...] = all_literal_values(type_)
     allowed_choices_set = set(permitted_choices)
 
     def literal_validator(v: Any) -> Any:
diff --git a/tests/test_validators.py b/tests/test_validators.py
index 470ed4a2bb9..4b2fe35b0a6 100644
--- a/tests/test_validators.py
+++ b/tests/test_validators.py
@@ -7,7 +7,7 @@
 from pydantic import BaseModel, ConfigError, Extra, ValidationError, errors, validator
 from pydantic.class_validators import make_generic_validator, root_validator
 from pydantic.typing import Literal
-from pydantic.validators import flatten_literal
+from pydantic.validators import all_literal_values
 
 
 def test_simple():
@@ -1086,11 +1086,11 @@ class Model(BaseModel):
 @pytest.mark.skipif(not Literal, reason='typing_extensions not installed')
 def test_flatten_nested_literals():
     L1 = Literal['1']
-    assert flatten_literal(L1) == ['1']
+    assert all_literal_values(L1) == ('1',)
 
     L2 = Literal['2']
     L12 = Literal[L1, L2]
-    assert sorted(flatten_literal(L12)) == sorted(['1', '2'])
+    assert sorted(all_literal_values(L12)) == sorted(('1', '2'))
 
     L312 = Literal['3', Literal[L1, L2]]
-    assert sorted(flatten_literal(L312)) == sorted(['1', '2', '3'])
+    assert sorted(all_literal_values(L312)) == sorted(('1', '2', '3'))