diff --git a/src/oid.c b/src/oid.c
index f1a6f52..ae91d04 100644
--- a/src/oid.c
+++ b/src/oid.c
@@ -200,6 +200,14 @@ Oid_init(Oid *self, PyObject *args, PyObject *kw)
 }
 
 
+Py_hash_t
+Oid_hash(PyObject *oid)
+{
+    /* TODO Randomize (use _Py_HashSecret) to avoid collission DoS attacks? */
+    return *(Py_hash_t*) ((Oid*)oid)->oid.id;
+}
+
+
 PyObject *
 Oid_richcompare(PyObject *o1, PyObject *o2, int op)
 {
@@ -279,7 +287,7 @@ PyTypeObject OidType = {
     0,                                         /* tp_as_number      */
     0,                                         /* tp_as_sequence    */
     0,                                         /* tp_as_mapping     */
-    0,                                         /* tp_hash           */
+    (hashfunc)Oid_hash,                        /* tp_hash           */
     0,                                         /* tp_call           */
     0,                                         /* tp_str            */
     0,                                         /* tp_getattro       */
diff --git a/src/utils.h b/src/utils.h
index 0dbe20b..2ce8074 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -54,6 +54,11 @@
   #define to_encoding(x) PyUnicode_DecodeASCII(x, strlen(x), "strict")
 #endif
 
+#ifndef Py_hash_t
+  #define Py_hash_t long
+#endif
+
+
 #define CHECK_REFERENCE(self)\
     if (self->reference == NULL) {\
         PyErr_SetString(GitError, "deleted reference");\
diff --git a/test/test_oid.py b/test/test_oid.py
index 97c7979..5e6b223 100644
--- a/test/test_oid.py
+++ b/test/test_oid.py
@@ -94,6 +94,16 @@ class OidTest(utils.BareRepoTestCase):
         self.assertFalse(oid1 > oid2)
         self.assertFalse(oid1 >= oid2)
 
+    def test_hash(self):
+        s = set()
+        s.add(Oid(raw=RAW))
+        s.add(Oid(hex=HEX))
+        self.assertEqual(len(s), 1)
+
+        s.add(Oid(hex="0000000000000000000000000000000000000000"))
+        s.add(Oid(hex="0000000000000000000000000000000000000001"))
+        self.assertEqual(len(s), 3)
+
 
 if __name__ == '__main__':
     unittest.main()