diff --git a/jedi/evaluate/compiled/__init__.py b/jedi/evaluate/compiled/__init__.py
index e0401b57..9cb49d71 100644
--- a/jedi/evaluate/compiled/__init__.py
+++ b/jedi/evaluate/compiled/__init__.py
@@ -100,37 +100,18 @@ class CompiledObject(Context):
         return self.access.py__doc__()
 
     def get_param_names(self):
-        obj = self.obj
         try:
-            if py_version < 33:
-                raise ValueError("inspect.signature was introduced in 3.3")
-            if py_version == 34:
-                # In 3.4 inspect.signature are wrong for str and int. This has
-                # been fixed in 3.5. The signature of object is returned,
-                # because no signature was found for str. Here we imitate 3.5
-                # logic and just ignore the signature if the magic methods
-                # don't match object.
-                # 3.3 doesn't even have the logic and returns nothing for str
-                # and classes that inherit from object.
-                user_def = inspect._signature_get_user_defined_method
-                if (inspect.isclass(obj)
-                        and not user_def(type(obj), '__init__')
-                        and not user_def(type(obj), '__new__')
-                        and (obj.__init__ != object.__init__
-                             or obj.__new__ != object.__new__)):
-                    raise ValueError
-
-            signature = inspect.signature(obj)
+            signature_params = self.access.get_signature_params()
         except ValueError:  # Has no signature
             params_str, ret = self._parse_function_doc()
             tokens = params_str.split(',')
-            if inspect.ismethoddescriptor(obj):
+            if self.access.ismethoddescriptor():
                 tokens.insert(0, 'self')
             for p in tokens:
                 parts = p.strip().split('=')
                 yield UnresolvableParamName(self, parts[0])
         else:
-            for signature_param in signature.parameters.values():
+            for signature_param in signature_params.values():
                 yield SignatureParamName(self, signature_param)
 
     def __repr__(self):
diff --git a/jedi/evaluate/compiled/access.py b/jedi/evaluate/compiled/access.py
index bf884c9f..f3e87ec4 100644
--- a/jedi/evaluate/compiled/access.py
+++ b/jedi/evaluate/compiled/access.py
@@ -1,8 +1,9 @@
 import inspect
 import types
 import operator as op
+from collections import namedtuple
 
-from jedi._compatibility import unicode, is_py3, is_py34, builtins
+from jedi._compatibility import unicode, is_py3, is_py34, builtins, py_version
 from jedi.evaluate.compiled.getattr_static import getattr_static
 
 
@@ -72,6 +73,7 @@ _OPERATORS = {
 _OPERATORS.update(COMPARISON_OPERATORS)
 
 
+SignatureParam = namedtuple('SignatureParam', 'name default empty annotation')
 
 
 class DirectObjectAccess(object):
@@ -142,6 +144,9 @@ class DirectObjectAccess(object):
     def is_class(self):
         return inspect.isclass(self._obj)
 
+    def ismethoddescriptor(self):
+        return inspect.ismethoddescriptor(self._obj)
+
     def dir(self):
         return dir(self._obj)
 
@@ -242,6 +247,36 @@ class DirectObjectAccess(object):
     def needs_type_completions(self):
         return inspect.isclass(self._obj) and self._obj != type
 
+    def get_signature_params(self):
+        obj = self._obj
+        if py_version < 33:
+            raise ValueError("inspect.signature was introduced in 3.3")
+        if py_version == 34:
+            # In 3.4 inspect.signature are wrong for str and int. This has
+            # been fixed in 3.5. The signature of object is returned,
+            # because no signature was found for str. Here we imitate 3.5
+            # logic and just ignore the signature if the magic methods
+            # don't match object.
+            # 3.3 doesn't even have the logic and returns nothing for str
+            # and classes that inherit from object.
+            user_def = inspect._signature_get_user_defined_method
+            if (inspect.isclass(obj)
+                    and not user_def(type(obj), '__init__')
+                    and not user_def(type(obj), '__new__')
+                    and (obj.__init__ != object.__init__
+                         or obj.__new__ != object.__new__)):
+                raise ValueError
+
+        signature = inspect.signature(obj)
+        return [
+            SignatureParam(
+                name=p.name,
+                default=p.default,
+                empty=p.empty,
+                annotation=p.annotation,
+            ) for p in signature.parameters
+        ]
+
 
 def is_class_instance(obj):
     """Like inspect.* methods."""