diff --git a/cli/koji_cli/commands.py b/cli/koji_cli/commands.py
index 7ec7182d..51e5e334 100644
--- a/cli/koji_cli/commands.py
+++ b/cli/koji_cli/commands.py
@@ -24,6 +24,7 @@ import koji
 from koji.util import base64encode, md5_constructor, to_list
 from koji_cli.lib import (
     TimeOption,
+    DatetimeJSONEncoder,
     _,
     _list_tasks,
     _progress_callback,
@@ -1045,7 +1046,7 @@ def handle_call(goptions, session, args):
                 non_kw.append(arg_filter(arg))
     response = getattr(session, name).__call__(*non_kw, **kw)
     if options.json_output:
-        print(json.dumps(response, indent=2, separators=(',', ': ')))
+        print(json.dumps(response, indent=2, separators=(',', ': '), cls=DatetimeJSONEncoder))
     else:
         pprint.pprint(response)
 
diff --git a/cli/koji_cli/lib.py b/cli/koji_cli/lib.py
index bb80ca7f..4ba7dd6c 100644
--- a/cli/koji_cli/lib.py
+++ b/cli/koji_cli/lib.py
@@ -9,6 +9,7 @@ import socket
 import string
 import sys
 import time
+import json
 from contextlib import closing
 from copy import copy
 
@@ -21,6 +22,7 @@ import koji
 # import parse_arches to current namespace for backward compatibility
 from koji import parse_arches
 from koji.util import md5_constructor, to_list
+from koji.xmlrpcplus import xmlrpc_client
 
 
 # for compatibility with plugins based on older version of lib
@@ -848,3 +850,10 @@ def truncate_string(s, length=47):
             return s
     else:
         return ''
+
+
+class DatetimeJSONEncoder(json.JSONEncoder):
+    def default(self, o):
+        if isinstance(o, xmlrpc_client.DateTime):
+            return str(o)
+        return json.JSONEncoder.default(self, o)