diff --git a/.isort.cfg b/.isort.cfg
index 4d4a6a509..6a749cf25 100644
--- a/.isort.cfg
+++ b/.isort.cfg
@@ -1,5 +1,5 @@
 [settings]
-skip=.tox
+skip=.tox,tests/compat/compat_py35.py
 atomic=true
 multi_line_output=5
 known_standard_library=types
diff --git a/rest_framework/compat.py b/rest_framework/compat.py
index dd30636f4..227313bd0 100644
--- a/rest_framework/compat.py
+++ b/rest_framework/compat.py
@@ -7,6 +7,7 @@ versions of Django/Python, and compatibility wrappers around optional packages.
 from __future__ import unicode_literals
 
 import inspect
+import sys
 
 import django
 from django.apps import apps
@@ -206,11 +207,34 @@ if six.PY3:
     SHORT_SEPARATORS = (',', ':')
     LONG_SEPARATORS = (', ', ': ')
     INDENT_SEPARATORS = (',', ': ')
+
 else:
     SHORT_SEPARATORS = (b',', b':')
     LONG_SEPARATORS = (b', ', b': ')
     INDENT_SEPARATORS = (b',', b': ')
 
+
+def is_simple_callable(obj):
+    """
+    True if the object is a callable that takes no arguments.
+    """
+
+    function = inspect.isfunction(obj)
+    method = inspect.ismethod(obj)
+
+    if not (function or method):
+        return False
+    if sys.version_info >= (3, 3):
+        signature = inspect.signature(obj)
+        defaults = [p for p in signature.parameters.values() if p.default is not inspect.Parameter.empty]
+        return len(signature.parameters) <= len(defaults)
+    else:
+        function = inspect.isfunction(obj)
+        args, _, _, defaults = inspect.getargspec(obj)
+        len_args = len(args) if function else len(args) - 1
+        len_defaults = len(defaults) if defaults else 0
+        return len_args <= len_defaults
+
 try:
     # DecimalValidator is unavailable in Django < 1.9
     from django.core.validators import DecimalValidator
diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 68e4cdf91..c220b2031 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -31,7 +31,7 @@ from django.utils.translation import ugettext_lazy as _
 
 from rest_framework import ISO_8601
 from rest_framework.compat import (
-    get_remote_field, unicode_repr, unicode_to_repr, value_from_object
+    get_remote_field, is_simple_callable, unicode_repr, unicode_to_repr, value_from_object
 )
 from rest_framework.exceptions import ValidationError
 from rest_framework.settings import api_settings
@@ -48,22 +48,6 @@ class empty:
     pass
 
 
-def is_simple_callable(obj):
-    """
-    True if the object is a callable that takes no arguments.
-    """
-    function = inspect.isfunction(obj)
-    method = inspect.ismethod(obj)
-
-    if not (function or method):
-        return False
-
-    args, _, _, defaults = inspect.getargspec(obj)
-    len_args = len(args) if function else len(args) - 1
-    len_defaults = len(defaults) if defaults else 0
-    return len_args <= len_defaults
-
-
 def get_attribute(instance, attrs):
     """
     Similar to Python's built in `getattr(instance, attr)`,
diff --git a/rest_framework/relations.py b/rest_framework/relations.py
index 2e7c51b22..96bfe71cd 100644
--- a/rest_framework/relations.py
+++ b/rest_framework/relations.py
@@ -14,9 +14,8 @@ from django.utils.encoding import smart_text
 from django.utils.six.moves.urllib import parse as urlparse
 from django.utils.translation import ugettext_lazy as _
 
-from rest_framework.fields import (
-    Field, empty, get_attribute, is_simple_callable, iter_options
-)
+from rest_framework.compat import is_simple_callable
+from rest_framework.fields import Field, empty, get_attribute, iter_options
 from rest_framework.reverse import reverse
 from rest_framework.utils import html
 
diff --git a/tests/compat/__init__.py b/tests/compat/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/compat/compat_py35.py b/tests/compat/compat_py35.py
new file mode 100644
index 000000000..8265f2658
--- /dev/null
+++ b/tests/compat/compat_py35.py
@@ -0,0 +1,21 @@
+# for now, linting is done by python2.7, so for that file it should be disabled.
+# flake8: noqa
+
+
+class FunctionSimplicityCheckPy35Mixin:
+    def get_good_cases(self):
+        def annotated_simple() -> int:
+            return 0
+
+        def annotated_defaults(x: int = 0) -> int:
+            return 0
+
+        def kwonly_defaults(*, x=0):
+            pass
+        return super().get_good_cases() + (annotated_simple, annotated_defaults, kwonly_defaults)
+
+    def get_bad_cases(self):
+        def kwonly(*, x):
+            pass
+
+        return super().get_bad_cases() + (kwonly,)
diff --git a/tests/test_compat.py b/tests/test_compat.py
new file mode 100644
index 000000000..974b9ba25
--- /dev/null
+++ b/tests/test_compat.py
@@ -0,0 +1,52 @@
+from __future__ import unicode_literals
+
+import sys
+
+from rest_framework.compat import is_simple_callable
+
+
+class TestFunctionSimplicityCheck:
+    def get_good_cases(self):
+        def simple():
+            pass
+
+        def simple_with_default(x=0):
+            pass
+
+        class SimpleMethods(object):
+            def simple(self):
+                pass
+
+            def simple_with_default(self, x=0):
+                pass
+
+        return simple, simple_with_default, SimpleMethods().simple, SimpleMethods().simple_with_default
+
+    def get_bad_cases(self):
+        def positional(x):
+            pass
+
+        def many_positional_and_defaults(x, y, z=0):
+            pass
+
+        nofunc = 0
+
+        class Callable:
+            pass
+
+        return positional, many_positional_and_defaults, nofunc, Callable
+
+    def test_good_cases(self):
+        for case in self.get_good_cases():
+            assert is_simple_callable(case)
+
+    def test_bad_cases(self):
+        for case in self.get_bad_cases():
+            assert not is_simple_callable(case)
+
+
+if sys.version_info >= (3, 5):
+    from tests.compat.compat_py35 import FunctionSimplicityCheckPy35Mixin
+
+    class TestFunctionSimplicityCheckPy35(FunctionSimplicityCheckPy35Mixin, TestFunctionSimplicityCheck):
+        pass