diff --git a/git_trace2_event_log_base.py b/git_trace2_event_log_base.py
index 1a59fee8a..063d101c6 100644
--- a/git_trace2_event_log_base.py
+++ b/git_trace2_event_log_base.py
@@ -195,7 +195,13 @@ class BaseEventLog:
 
     def GetDataEventName(self, value):
         """Returns 'data-json' if the value is an array else returns 'data'."""
-        return "data-json" if value[0] == "[" and value[-1] == "]" else "data"
+        return (
+            "data-json"
+            if isinstance(value, str)
+            and value.startswith("[")
+            and value.endswith("]")
+            else "data"
+        )
 
     def LogDataConfigEvents(self, config, prefix):
         """Append a 'data' event for each entry in |config| to the current log.
diff --git a/tests/test_git_trace2_event_log.py b/tests/test_git_trace2_event_log.py
index 9a6ba2052..13b64df2d 100644
--- a/tests/test_git_trace2_event_log.py
+++ b/tests/test_git_trace2_event_log.py
@@ -315,6 +315,7 @@ def test_data_event_config(event_log: git_trace2_event_log.EventLog) -> None:
         "repo.partialclone": "false",
         "repo.syncstate.superproject.hassuperprojecttag": "true",
         "repo.syncstate.superproject.sys.argv": ["--", "sync", "protobuf"],
+        "repo.syncstate.emptykey": "",
     }
     prefix_value = "prefix"
     event_log.LogDataConfigEvents(config, prefix_value)
@@ -323,7 +324,7 @@ def test_data_event_config(event_log: git_trace2_event_log.EventLog) -> None:
         log_path = event_log.Write(path=tempdir)
         log_data = read_log(log_path)
 
-    assert len(log_data) == 5
+    assert len(log_data) == 6
     data_events = log_data[1:]
     verify_common_keys(log_data[0], expected_event_name="version")