diff --git a/git_trace2_event_log.py b/git_trace2_event_log.py
index 46bd5e4b..5b99867b 100644
--- a/git_trace2_event_log.py
+++ b/git_trace2_event_log.py
@@ -203,8 +203,8 @@ class EventLog(object):
         error_event = self._CreateEventDict("error")
         if fmt is None:
             fmt = msg
-        error_event["msg"] = msg
-        error_event["fmt"] = fmt
+        error_event["msg"] = f"RepoErrorEvent:{msg}"
+        error_event["fmt"] = f"RepoErrorEvent:{fmt}"
         self._log.append(error_event)
 
     def _GetEventTargetPath(self):
diff --git a/tests/test_git_trace2_event_log.py b/tests/test_git_trace2_event_log.py
index a6078d38..9d4f24c3 100644
--- a/tests/test_git_trace2_event_log.py
+++ b/tests/test_git_trace2_event_log.py
@@ -338,8 +338,8 @@ class EventLogTestCase(unittest.TestCase):
         # Check for 'error' event specific fields.
         self.assertIn("msg", error_event)
         self.assertIn("fmt", error_event)
-        self.assertEqual(error_event["msg"], msg)
-        self.assertEqual(error_event["fmt"], fmt)
+        self.assertEqual(error_event["msg"], f"RepoErrorEvent:{msg}")
+        self.assertEqual(error_event["fmt"], f"RepoErrorEvent:{fmt}")
 
     def test_write_with_filename(self):
         """Test Write() with a path to a file exits with None."""