@@ -130,7 +130,8 @@ def __init__(self, repo, binsha, tree=None, author=None, authored_date=None, aut
             self.parents = parents
         if encoding is not None:
             self.encoding = encoding
-        self.gpgsig = gpgsig
+        if gpgsig is not None:
+            self.gpgsig = gpgsig
 
     @classmethod
     def _get_intermediate_items(cls, commit):
@@ -425,10 +426,13 @@ def _serialize(self, stream):
         if self.encoding != self.default_encoding:
             write(("encoding %s\n" % self.encoding).encode('ascii'))
 
-        if self.gpgsig:
-            write(b"gpgsig")
-            for sigline in self.gpgsig.rstrip("\n").split("\n"):
-                write((" " + sigline + "\n").encode('ascii'))
+        try:
+            if self.__getattribute__('gpgsig') is not None:
+                write(b"gpgsig")
+                for sigline in self.gpgsig.rstrip("\n").split("\n"):
+                    write((" " + sigline + "\n").encode('ascii'))
+        except AttributeError:
+            pass
 
         write(b"\n")
 
@@ -473,6 +477,7 @@ def _deserialize(self, stream):
         # now we can have the encoding line, or an empty line followed by the optional
         # message.
         self.encoding = self.default_encoding
+        self.gpgsig = None
 
         # read headers
         enc = next_line
 
@@ -34,6 +34,7 @@
 import os
 from datetime import datetime
 from git.objects.util import tzoffset, utc
+from mock import Mock
 
 
 def assert_commit_serialization(rwrepo, commit_id, print_performance_info=False):
@@ -342,7 +343,9 @@ def test_gpgsig(self):
         cstream = BytesIO()
         cmt._serialize(cstream)
         assert re.search(r"^gpgsig <test\n dummy\n sig>$", cstream.getvalue().decode('ascii'), re.MULTILINE)
-
+        
+        self.assert_gpgsig_deserialization(cstream)
+        
         cstream.seek(0)
         cmt.gpgsig = None
         cmt._deserialize(cstream)
@@ -352,6 +355,31 @@ def test_gpgsig(self):
         cstream = BytesIO()
         cmt._serialize(cstream)
         assert not re.search(r"^gpgsig ", cstream.getvalue().decode('ascii'), re.MULTILINE)
+        
+    def assert_gpgsig_deserialization(self, cstream):
+        assert 'gpgsig' in 'precondition: need gpgsig'
+        
+        class RepoMock:
+            def __init__(self, bytestr):
+                self.bytestr = bytestr
+                
+            @property
+            def odb(self):
+                class ODBMock:
+                    def __init__(self, bytestr):
+                        self.bytestr = bytestr
+                        
+                    def stream(self, *args):
+                        stream = Mock(spec_set=['read'], return_value=self.bytestr)
+                        stream.read.return_value = self.bytestr
+                        return ('binsha', 'typename', 'size', stream)
+                        
+                return ODBMock(self.bytestr)
+                    
+        repo_mock = RepoMock(cstream.getvalue())
+        for field in Commit.__slots__:
+            c = Commit(repo_mock, b'x' * 20)
+            assert getattr(c, field) is not None
 
     def test_datetimes(self):
         commit = self.rorepo.commit('4251bd5')