diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 5dcc98424ac08b64187015a0a295874be5d316cc..8d41c0d79909a7dd42b8050de88d1e3c275e2148 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -16,7 +16,7 @@ def collection_cache_key(collection = all, timestamp_column = :updated_at) # :no
 
         query = collection
           .unscope(:select)
-          .select("COUNT(*) AS size", "MAX(#{column}) AS timestamp")
+          .select("COUNT(*) AS #{connection.quote_column_name("size")}", "MAX(#{column}) AS timestamp")
           .unscope(:order)
         result = connection.select_one(query)