diff --git a/jedi/api/__init__.py b/jedi/api/__init__.py
index c44c6c25..ff75b271 100644
--- a/jedi/api/__init__.py
+++ b/jedi/api/__init__.py
@@ -494,7 +494,7 @@ class Script(object):
             origins = cache.cache_call_signatures(_callable, user_stmt)
         debug.speed('func_call followed')
 
-        return [classes.CallSignature(self._evaluator, o, index, call) for o in origins
+        return [classes.CallSignature(self._evaluator, o, call, index) for o in origins
                 if o.isinstance(er.Function, er.Instance, er.Class)
                 or isinstance(o, compiled.CompiledObject) and o.type() != 'module']
 
diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 9839c302..664beddc 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -547,7 +547,7 @@ class CallSignature(object):
     It knows what functions you are currently in. e.g. `isinstance(` would
     return the `isinstance` function. without `(` it would return nothing.
     """
-    def __init__(self, evaluator, executable, index, call):
+    def __init__(self, evaluator, executable, call, index):
         self._evaluator = evaluator
         self._executable = executable
         self.index = index
@@ -572,8 +572,10 @@ class CallSignature(object):
 
     @property
     def bracket_start(self):
-        """ The indent of the bracket that is responsible for the last function
-        call. """
+        """
+        The indent of the bracket that is responsible for the last function
+        call.
+        """
         c = self._call
         while c.next is not None:
             c = c.next
diff --git a/test/test_api/test_call_signatures.py b/test/test_api/test_call_signatures.py
index 225c3e72..c32a18e6 100644
--- a/test/test_api/test_call_signatures.py
+++ b/test/test_api/test_call_signatures.py
@@ -2,6 +2,7 @@ import textwrap
 
 from ..helpers import TestCase
 from jedi import Script
+from jedi._compatibility import is_py33
 
 
 class TestCallSignatures(TestCase):
@@ -167,7 +168,12 @@ class TestParams(TestCase):
         return signatures[0].params
 
     def test_param_name(self):
-        p = self.params('''int(''')
-        # int is defined as: `int(x[, base])`
-        assert p[0].name == 'x'
-        assert p[1].name == 'base'
+        if not is_py33:
+            p = self.params('''int(''')
+            # int is defined as: `int(x[, base])`
+            assert p[0].name == 'x'
+            assert p[1].name == 'base'
+
+        p = self.params('''open(something,''')
+        assert p[0].name in ['file', 'name']
+        assert p[1].name == 'mode'