diff --git a/Lib/inspect.py b/Lib/inspect.py
index c9d10dc..ee77b3d 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -951,9 +951,54 @@ def getfullargspec(func):
         func = func.__func__
     if not isfunction(func):
         raise TypeError('{!r} is not a Python function'.format(func))
-    args, varargs, kwonlyargs, varkw = _getfullargs(func.__code__)
-    return FullArgSpec(args, varargs, varkw, func.__defaults__,
-            kwonlyargs, func.__kwdefaults__, func.__annotations__)
+
+    sig = signature(func)
+
+    args = []
+    varargs = None
+    varkw = None
+    kwonlyargs = []
+    defaults = ()
+    annotations = {}
+    defaults = ()
+    kwdefaults = {}
+
+    if sig.return_annotation is not sig.empty:
+        annotations['return'] = sig.return_annotation
+
+    for param in sig.parameters.values():
+        kind = param.kind
+        name = param.name
+
+        if kind is _POSITIONAL_ONLY:
+            args.append(name)
+        elif kind is _POSITIONAL_OR_KEYWORD:
+            args.append(name)
+            if param.default is not param.empty:
+                defaults += (param.default,)
+        elif kind is _VAR_POSITIONAL:
+            varargs = name
+        elif kind is _KEYWORD_ONLY:
+            kwonlyargs.append(name)
+            if param.default is not param.empty:
+                kwdefaults[name] = param.default
+        elif kind is _VAR_KEYWORD:
+            varkw = name
+
+        if param.annotation is not param.empty:
+            annotations[name] = param.annotation
+
+    if not kwdefaults:
+        # compatibility with 'func.__kwdefaults__'
+        kwdefaults = None
+
+    if not defaults:
+        # compatibility with 'func.__defaults__'
+        defaults = None
+
+    return FullArgSpec(args, varargs, varkw, defaults,
+                       kwonlyargs, kwdefaults, annotations)
+
 
 ArgInfo = namedtuple('ArgInfo', 'args varargs keywords locals')
 
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 9dc5475..914f0cb 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -566,6 +566,13 @@ class TestClassesAndFunctions(unittest.TestCase):
                                      kwonlyargs_e=['arg'],
                                      formatted='(*, arg)')
 
+    def test_getfullargspec_signature(self):
+        def test():
+            pass
+        spam_param = inspect.Parameter('spam', inspect.Parameter.POSITIONAL_ONLY)
+        test.__signature__ = inspect.Signature(parameters=(spam_param,))
+
+        self.assertFullArgSpecEquals(test, args_e=['spam'], formatted='(spam)')
 
     def test_getargspec_method(self):
         class A(object):