diff --git a/jedi/utils.py b/jedi/utils.py
index af6b8eb3..74ba7ebd 100644
--- a/jedi/utils.py
+++ b/jedi/utils.py
@@ -10,7 +10,7 @@ from jedi._compatibility import builtins
 from jedi import Interpreter
 
 
-def setup_readline():
+def setup_readline(namespace=__main__.__dict__):
     """
     Install Jedi completer to :mod:`readline`.
 
@@ -68,7 +68,6 @@ def setup_readline():
                 library module.
                 """
                 if state == 0:
-                    namespace = __main__.__dict__
                     interpreter = Interpreter(text, [namespace])
 
                     # The following part is a bit hackish, because it tries to
@@ -76,20 +75,20 @@ def setup_readline():
                     # use the "default" completion with ``getattr`` if
                     # possible.
                     path, dot, like = interpreter._get_completion_parts()
-                    if re.match('^[\w][\w\d.]*$', path):
+                    if not path or re.match('^[\w][\w\d.]*$', path):
                         paths = path.split('.') if path else []
-                        namespaces = (namespace, builtins)
+                        namespaces = (namespace, builtins.__dict__)
                         for p in paths:
                             old, namespaces = namespaces, []
                             for n in old:
                                 try:
-                                    namespaces.append(getattr(n, p))
-                                except AttributeError:
+                                    namespaces.append(n[p].__dict__)
+                                except (KeyError, AttributeError):
                                     pass
 
                         self.matches = []
                         for n in namespaces:
-                            for name in dir(n):
+                            for name in n.keys():
                                 if name.lower().startswith(like.lower()):
                                     self.matches.append(path + dot + name)
                     else:
@@ -101,8 +100,6 @@ def setup_readline():
                     return None
 
         readline.set_completer(JediRL().complete)
-        j = JediRL()
-        j.complete('r', 0)
 
         readline.parse_and_bind("tab: complete")
         # No delimiters, Jedi handles that.
diff --git a/test/test_utils.py b/test/test_utils.py
new file mode 100644
index 00000000..1e796452
--- /dev/null
+++ b/test/test_utils.py
@@ -0,0 +1,59 @@
+import readline
+
+from jedi import utils
+
+
+class TestSetupReadline():
+    namespace = dict()
+    utils.setup_readline(namespace)
+
+    def completions(self, text):
+        completer = readline.get_completer()
+        i = 0
+        completions = []
+        while True:
+            completion = completer(text, i)
+            if completion is None:
+                break
+            completions.append(completion)
+            i += 1
+        return completions
+
+    def test_simple(self):
+        assert self.completions('list') == ['list']
+        assert self.completions('importerror') == ['ImportError']
+
+    def test_nested(self):
+        assert self.completions('list.Insert') == ['list.insert']
+        assert self.completions('list().Insert') == ['list().insert']
+
+    def test_magic_methods(self):
+        assert self.completions('list.__getitem__') == ['list.__getitem__']
+        assert self.completions('list().__getitem__') == ['list().__getitem__']
+
+    def test_modules(self):
+        import sys
+        import os
+        self.namespace['sys'] = sys
+        self.namespace['os'] = os
+
+        c = set(['os.' + d for d in dir(os) if d.startswith('ch')])
+        assert set(self.completions('os.ch')) == set(c)
+        assert self.completions('os.chdir') == ['os.chdir']
+        assert self.completions('os.path.join') == ['os.path.join']
+        assert self.completions('os.path.join().upper') == ['os.path.join().upper']
+
+        del self.namespace['sys']
+        del self.namespace['os']
+
+    def test_colorama(self):
+        """Only test it if colorama library is available"""
+        try:
+            # if colorama is installed
+            import colorama
+        except ImportError:
+            pass
+        else:
+            self.namespace['colorama'] = colorama
+            assert self.completions('colorama')
+            del self.namespace['colorama']