diff --git a/koji/plugin.py b/koji/plugin.py
index 6191f2e2..396b8111 100644
--- a/koji/plugin.py
+++ b/koji/plugin.py
@@ -200,6 +200,16 @@ def run_callbacks(cbtype, *args, **kws):
 
 def _fix_cb_args(func, args, kwargs, cache):
     if getattr(func, 'convert_datetime', False):
-        args = encode_datetime_recurse(args)
-        kwargs = encode_datetime_recurse(kwargs)
+        if id(args) in cache:
+            args = cache[id(args)]
+        else:
+            val = encode_datetime_recurse(args)
+            cache[id(args)] = val
+            args = val
+        if id(kwargs) in cache:
+            kwargs = cache[id(kwargs)]
+        else:
+            val = encode_datetime_recurse(kwargs)
+            cache[id(kwargs)] = val
+            kwargs = val
     return args, kwargs
diff --git a/tests/test_lib/test_plugin.py b/tests/test_lib/test_plugin.py
index ea24be33..f064a5d3 100644
--- a/tests/test_lib/test_plugin.py
+++ b/tests/test_lib/test_plugin.py
@@ -104,6 +104,10 @@ class TestCallbacks(unittest.TestCase):
     def datetime_callback(self, cbtype, *args, **kwargs):
         self.callbacks.append([cbtype, args, kwargs])
 
+    @koji.plugin.convert_datetime
+    def datetime_callback2(self, cbtype, *args, **kwargs):
+        self.callbacks.append([cbtype, args, kwargs])
+
     def test_simple_callback(self):
         args = ('hello',)
         kwargs = {'world': 1}
@@ -146,6 +150,34 @@ class TestCallbacks(unittest.TestCase):
         self.assertEqual(len(self.callbacks), 1)
         self.assertEqual(self.callbacks[0], [cbtype, args2, kwargs2])
 
+    def test_multiple_datetime_callback(self):
+        dt1 = datetime.datetime.now()
+        dt2 = datetime.datetime(2001,1,1)
+        args = (dt1,"2",["three"], {4: dt2},)
+        kwargs = {'foo': [dt1, dt2]}
+        cbtype = 'preTag'
+        koji.plugin.register_callback(cbtype, self.datetime_callback)
+        koji.plugin.register_callback(cbtype, self.datetime_callback2)
+        koji.plugin.run_callbacks(cbtype, *args, **kwargs)
+        args2 = koji.util.encode_datetime_recurse(args)
+        kwargs2 = koji.util.encode_datetime_recurse(kwargs)
+        self.assertEqual(len(self.callbacks), 2)
+        self.assertEqual(self.callbacks[0], [cbtype, args2, kwargs2])
+        self.assertEqual(self.callbacks[1], [cbtype, args2, kwargs2])
+        # verify that caching worked
+        # unfortunately, args and kwargs get unpacked and repacked, so we have
+        # to dig down
+        cb_args1 = self.callbacks[0][1]
+        cb_args2 = self.callbacks[1][1]
+        for i in range(len(cb_args1)):
+            if cb_args1[i] is not cb_args2[i]:
+                raise Exception("converted args not cached")
+        cb_kwargs1 = self.callbacks[0][2]
+        cb_kwargs2 = self.callbacks[1][2]
+        for k in cb_kwargs1:
+            if cb_kwargs1[k] is not cb_kwargs2[k]:
+                raise Exception("converted kwargs not cached")
+
     def test_bad_callback(self):
         args = ('hello',)
         kwargs = {'world': 1}