diff --git a/rest_framework/compat.py b/rest_framework/compat.py
index 759cd1fbc..2a6af4c5c 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.conf import settings
@@ -139,37 +140,28 @@ if six.PY3:
     LONG_SEPARATORS = (', ', ': ')
     INDENT_SEPARATORS = (',', ': ')
 
-    def is_simple_callable(obj):
-        function = inspect.isfunction(obj)
-        method = inspect.ismethod(obj)
-
-        if not (function or method):
-            return False
-        # when we drop support of python3.2, we should replace getfullargspec with singnature
-        # 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)
-        function = inspect.isfunction(obj)
-        args, _, _, defaults, _, kwonly, kwdefaults = inspect.getfullargspec(obj)
-        len_args = (len(args) if function else len(args) - 1) + len(kwonly or ()) + len(kwdefaults or ())
-        len_defaults = (len(defaults) if defaults else 0) + len(kwdefaults or ())
-        return len_args <= len_defaults
-
 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.
-        """
+
+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)
-        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
diff --git a/tests/compat/test_compat_py35.py b/tests/compat/compat_py35.py
similarity index 100%
rename from tests/compat/test_compat_py35.py
rename to tests/compat/compat_py35.py
diff --git a/tests/test_compat.py b/tests/test_compat.py
index b0c40ce34..a93ccd398 100644
--- a/tests/test_compat.py
+++ b/tests/test_compat.py
@@ -47,7 +47,7 @@ class TestFunctionSimplicityCheck:
 
 
 if sys.version_info >= (3, 5):
-    from tests.compat.test_compat_py35 import FunctionSimplicityCheckPy35Mixin
+    from tests.compat.compat_py35 import FunctionSimplicityCheckPy35Mixin
 
     class TestFunctionSimplicityCheckPy35(FunctionSimplicityCheckPy35Mixin, TestFunctionSimplicityCheck):
         pass