--- a/CHANGES.txt	Tue Jul 16 11:12:24 2024 -0400
+++ b/CHANGES.txt	Tue Jul 16 20:23:36 2024 -0400
@@ -16,12 +16,16 @@
 2025-XX-XX 2.5.0
 
 Fixed:
+
 - issue2551343 - Remove support for PySQLite. It is unmaintained
   and sqlite3 is used which is the default for a Python
   distribution.  (John Rouillard)
 - replace use of os.listdir with os.scandir. Performance
   improvement.  Using with Python 2 requires 'pip install
   scandir'. (John Rouillard)
+- issue2551131 - Return accept-patch if patch body not accepted
+  (415 code). Accept-Patch returned with acceptable values. (John
+  Rouillard)
 
 Features:
 

--- a/roundup/rest.py	Tue Jul 16 11:12:24 2024 -0400
+++ b/roundup/rest.py	Tue Jul 16 20:23:36 2024 -0400
@@ -2412,6 +2412,10 @@
                 except ValueError as msg:
                     output = self.error_obj(400, msg)
             else:
+                if method.upper() == "PATCH":
+                    self.client.setHeader("Accept-Patch",
+                                          "application/json, "
+                                          "application/x-www-form-urlencoded")
                 output = self.error_obj(415,
                                 "Unable to process input of type %s" %
                                 content_type_header)

--- a/test/rest_common.py	Tue Jul 16 11:12:24 2024 -0400
+++ b/test/rest_common.py	Tue Jul 16 20:23:36 2024 -0400
@@ -1807,6 +1807,24 @@
         json_dict = json.loads(b2s(results))
         self.assertEqual(json_dict['error']['msg'],
                          "Unable to process input of type application/jzot")
+        self.assertNotIn("Accept-Patch",
+                         self.server.client.additional_headers)
+        self.server.client.additional_headers = {}
+
+
+        # test with PATCH verb to verify Accept-Patch is correct
+        results = self.server.dispatch("PATCH",
+                            "/rest/data/issue",
+                            form)
+        self.assertEqual(self.server.client.response_code, 415)
+        json_dict = json.loads(b2s(results))
+        self.assertEqual(json_dict['error']['msg'],
+                         "Unable to process input of type application/jzot")
+        self.assertIn("Accept-Patch",
+                         self.server.client.additional_headers)
+        self.assertEqual(self.server.client.additional_headers["Accept-Patch"],
+                        "application/json, application/x-www-form-urlencoded" )
+        self.server.client.additional_headers = {}
 
         # Test GET as well. I am not sure if this should pass or not.
         # Arguably GET doesn't use any form/json input but....
@@ -1815,8 +1833,9 @@
                             form)
         print(results)
         self.assertEqual(self.server.client.response_code, 415)
-
-
+        self.assertNotIn("Accept-Patch",
+                         self.server.client.additional_headers)
+        self.server.client.additional_headers = {}
 
     def testDispatchBadAccept(self):
         # simulate: /rest/data/issue expect failure unknown accept settings