2 files changed, 24 insertions, 1 deletions

diff --git a/src/mailman_pgp/rest/lists.py b/src/mailman_pgp/rest/lists.py
index 251ed7a..708635f 100644
--- a/src/mailman_pgp/rest/lists.py
+++ b/src/mailman_pgp/rest/lists.py
@@ -186,8 +186,14 @@ class AListKey:
         except (ValueError, PGPError) as error:
             bad_request(response, str(error))
             return
+
+        key = values.pop('key')
+        if key.is_public:
+            bad_request(response, 'Cannot set a public key.')
+            return
+
         with transaction():
-            self._mlist.key = values.pop('key')
+            self._mlist.key = key
         accepted(response)
 
 
diff --git a/src/mailman_pgp/rest/tests/test_lists.py b/src/mailman_pgp/rest/tests/test_lists.py
index 5d7c6aa..cae3138 100644
--- a/src/mailman_pgp/rest/tests/test_lists.py
+++ b/src/mailman_pgp/rest/tests/test_lists.py
@@ -272,6 +272,23 @@ class TestListKey(TestCase):
                      method='PUT')
         self.assertEqual(cm.exception.code, 400)
 
+    def test_set_list_key_public(self):
+        new_key = load_key('rsa_1024.priv.asc')
+        with self.assertRaises(HTTPError) as cm:
+            call_api('http://localhost:9001/3.1/plugins/pgp/lists/'
+                     'test.example.com/key',
+                     data=dict(key=str(new_key.pubkey)),
+                     method='PUT')
+
+        self.assertEqual(cm.exception.code, 400)
+
+        json, response = call_api(
+                'http://localhost:9001/3.1/plugins/pgp/lists/'
+                'test.example.com/key')
+
+        key, _ = PGPKey.from_blob(json['key'])
+        self.assertEqual(key.fingerprint, self.list_key.fingerprint)
+
     def test_get_list_pubkey(self):
         json, response = call_api(
                 'http://localhost:9001/3.1/plugins/pgp/lists/'