diff --git a/README.rst b/README.rst
index afdeeb8..081972f 100644
--- a/README.rst
+++ b/README.rst
@@ -148,9 +148,8 @@ Creating commits
 Commits can be created by calling the ``create_commit`` method of the
 repository with the following parameters::
 
-    >>> from time import time
-    >>> author = Signature('Alice Author', 'alice@authors.tld', time(), 0)
-    >>> committer = Signature('Cecil Committer', 'cecil@committers.tld', time(), 0)
+    >>> author = Signature('Alice Author', 'alice@authors.tld')
+    >>> committer = Signature('Cecil Committer', 'cecil@committers.tld')
     >>> tree = repo.TreeBuilder().write()
     >>> repo.create_commit(
     ... 'refs/heads/master', # the name of the reference to update
diff --git a/src/pygit2/signature.c b/src/pygit2/signature.c
index 430f881..19a28cb 100644
--- a/src/pygit2/signature.c
+++ b/src/pygit2/signature.c
@@ -36,32 +36,26 @@
 int
 Signature_init(Signature *self, PyObject *args, PyObject *kwds)
 {
+    const char *keywords[] = {
+        "name", "email", "time", "offset", "encoding", NULL};
     PyObject *py_name;
-    char *name, *email, *encoding = NULL;
-    long long time;
-    int offset;
+    char *name, *email, *encoding = "ascii";
+    long long time = -1;
+    int offset = 0;
     int err;
     git_signature *signature;
 
-    if (kwds) {
-        PyErr_SetString(PyExc_TypeError,
-                        "Signature takes no keyword arguments");
-        return -1;
-    }
-
-    if (!PyArg_ParseTuple(args, "Os|Lis",
-                          &py_name, &email, &time, &offset, &encoding))
+    if (!PyArg_ParseTupleAndKeywords(
+            args, kwds, "Os|Lis", keywords,
+            &py_name, &email, &time, &offset, &encoding))
         return -1;
 
     name = py_str_to_c_str(py_name, encoding);
     if (name == NULL)
         return -1;
 
-    if (PySequence_Length(args) == 2) {
+    if (time == -1) {
         err = git_signature_now(&signature, name, email);
-    } else if (PySequence_Length(args) == 3) {
-        PyErr_SetString(PyExc_TypeError, "offset must be specified with time");
-        return -1;
     } else {
         err = git_signature_new(&signature, name, email, time, offset);
     }
diff --git a/test/test_commit.py b/test/test_commit.py
index 0884364..35ec65f 100644
--- a/test/test_commit.py
+++ b/test/test_commit.py
@@ -68,7 +68,9 @@ class CommitTest(utils.BareRepoTestCase):
         repo = self.repo
         message = 'New commit.\n\nMessage with non-ascii chars: ééé.\n'
         committer = Signature('John Doe', 'jdoe@example.com', 12346, 0)
-        author = Signature('J. David Ibáñez', 'jdavid@example.com', 12345, 0)
+        author = Signature(
+            'J. David Ibáñez', 'jdavid@example.com', 12345, 0,
+            encoding='utf-8')
         tree = '967fce8df97cc71722d3c2a5930ef3e6f1d27b12'
         tree_prefix = tree[:5]
         too_short_prefix = tree[:3]
diff --git a/test/test_signature.py b/test/test_signature.py
index 2b59c29..2917a49 100644
--- a/test/test_signature.py
+++ b/test/test_signature.py
@@ -37,26 +37,29 @@ from .utils import NoRepoTestCase
 class SignatureTest(NoRepoTestCase):
 
     def test_default(self):
-        signature = Signature('Foo Ibáñez', 'foo@example.com', 1322174594, 60)
+        signature = Signature(
+            'Foo', 'foo@example.com', 1322174594, 60)
         encoding = signature._encoding
-        self.assertEqual(encoding, 'utf-8')
+        self.assertEqual(encoding, 'ascii')
         self.assertEqual(signature.name, signature._name.decode(encoding))
         self.assertEqual(signature.name.encode(encoding), signature._name)
 
+    def test_ascii(self):
+        self.assertRaises(
+                UnicodeEncodeError, Signature, 'Foo Ibáñez', 'foo@example.com')
+
     def test_latin1(self):
         encoding = 'iso-8859-1'
-        signature = Signature('Foo Ibáñez', 'foo@example.com', 1322174594, 60,
-                              encoding)
+        signature = Signature(
+            'Foo Ibáñez', 'foo@example.com', encoding=encoding)
         self.assertEqual(encoding, signature._encoding)
         self.assertEqual(signature.name, signature._name.decode(encoding))
         self.assertEqual(signature.name.encode(encoding), signature._name)
 
     def test_now(self):
-        self.assertRaises(TypeError, Signature, 'Foo Ibáñez',
-                          'foo@example.com', 1322174594)
-        signature = Signature('Foo Ibáñez', 'foo@example.com')
-        encoding = signature._encoding
-        self.assertEqual(encoding, 'utf-8')
+        encoding = 'utf-8'
+        signature = Signature(
+            'Foo Ibáñez', 'foo@example.com', encoding=encoding)
         self.assertEqual(encoding, signature._encoding)
         self.assertEqual(signature.name, signature._name.decode(encoding))
         self.assertEqual(signature.name.encode(encoding), signature._name)