diff --git a/homeassistant/components/logbook/processor.py b/homeassistant/components/logbook/processor.py
index f617c8e7d73..e25faf090b6 100644
--- a/homeassistant/components/logbook/processor.py
+++ b/homeassistant/components/logbook/processor.py
@@ -204,13 +204,12 @@ def _humanify(
     include_entity_name = logbook_run.include_entity_name
     format_time = logbook_run.format_time
     memoize_new_contexts = logbook_run.memoize_new_contexts
-    memoize_context = context_lookup.setdefault
 
     # Process rows
     for row in rows:
         context_id_bin: bytes = row.context_id_bin
-        if memoize_new_contexts:
-            memoize_context(context_id_bin, row)
+        if memoize_new_contexts and context_id_bin not in context_lookup:
+            context_lookup[context_id_bin] = row
         if row.context_only:
             continue
         event_type = row.event_type