Index: Lib/test/test_dbm.py
===================================================================
--- Lib/test/test_dbm.py	(revision 85567)
+++ Lib/test/test_dbm.py	(working copy)
@@ -160,6 +160,17 @@
         self.assertRaises(KeyError, lambda: self.d[b'xxx'])
         self.d.close()
 
+    def test_iter(self):
+        self.d = dbm.open(self.filename, 'c')
+        a = [(b'a', b'b'), (b'12345678910', b'019237410982340912840198242')]
+        for k, v in a:
+            self.d[k] = v
+        # An iterator always starts with the first element.
+        self.assertEqual(sorted(k for k in self.d), sorted(self.d.keys()))
+        self.assertEqual(sorted(k for k in self.d), sorted(self.d.keys()))
+        for k in self.d:
+            break
+        self.assertEqual(sorted(k for k in self.d), sorted(self.d.keys()))
 
 def test_main():
     classes = [WhichDBTestCase]
Index: Lib/test/test_dbm_gnu.py
===================================================================
--- Lib/test/test_dbm_gnu.py	(revision 85567)
+++ Lib/test/test_dbm_gnu.py	(working copy)
@@ -33,6 +33,19 @@
             key = self.g.nextkey(key)
         self.assertRaises(KeyError, lambda: self.g['xxx'])
 
+    def test_iter(self):
+        self.g = gdbm.open(filename, 'c')
+        self.g['a'] = 'b'
+        self.g['12345678910'] = '019237410982340912840198242'
+        self.g[b'bytes'] = b'data'
+        key_set = set(self.g.keys())
+        # An iterator always starts with the first element.
+        self.assertEqual(key_set, {x for x in self.g})
+        self.assertEqual(key_set, {x for x in self.g})
+        for k in self.g:
+            break
+        self.assertEqual(key_set, {x for x in self.g})
+
     def test_error_conditions(self):
         # Try to open a non-existent database.
         unlink(filename)
Index: Modules/_gdbmmodule.c
===================================================================
--- Modules/_gdbmmodule.c	(revision 85567)
+++ Modules/_gdbmmodule.c	(working copy)
@@ -275,6 +275,12 @@
         0,                      /* sq_inplace_repeat */
 };
 
+static PyObject *
+dbm_iter(dbmobject *dbm)
+{
+    return PyObject_GetIter(dbm_keys(dbm, NULL));
+}
+
 PyDoc_STRVAR(dbm_firstkey__doc__,
 "firstkey() -> key\n\
 It's possible to loop over every key in the database using this method\n\
@@ -407,7 +413,7 @@
     0,                                  /*tp_clear*/
     0,                                  /*tp_richcompare*/
     0,                                  /*tp_weaklistoffset*/
-    0,                                  /*tp_iter*/
+    (getiterfunc)dbm_iter,              /*tp_iter*/
     0,                                  /*tp_iternext*/
     dbm_methods,                        /*tp_methods*/
 };
Index: Modules/_dbmmodule.c
===================================================================
--- Modules/_dbmmodule.c	(revision 85567)
+++ Modules/_dbmmodule.c	(working copy)
@@ -249,6 +249,12 @@
 };
 
 static PyObject *
+dbm_iter(dbmobject *dbm)
+{
+    return PyObject_GetIter(dbm_keys(dbm, NULL));
+}
+
+static PyObject *
 dbm_get(register dbmobject *dp, PyObject *args)
 {
     datum key, val;
@@ -354,7 +360,7 @@
     0,                        /*tp_clear*/
     0,                        /*tp_richcompare*/
     0,                        /*tp_weaklistoffset*/
-    0,                        /*tp_iter*/
+    (getiterfunc)dbm_iter,   /*tp_iter*/
     0,                        /*tp_iternext*/
     dbm_methods,          /*tp_methods*/
 };