diff --git a/lib/chrono_model/time_machine/timeline.rb b/lib/chrono_model/time_machine/timeline.rb
index 30daaf2..de6600f 100644
--- a/lib/chrono_model/time_machine/timeline.rb
+++ b/lib/chrono_model/time_machine/timeline.rb
@@ -59,7 +59,7 @@ def timeline(record = nil, options = {})
         relation = relation.from("public.#{quoted_table_name}") unless chrono?
         relation = relation.where(id: rid) if rid
 
-        sql = +"SELECT ts FROM ( #{relation.to_sql} ) AS foo WHERE ts IS NOT NULL"
+        sql = "SELECT ts FROM ( #{relation.to_sql} ) AS foo WHERE ts IS NOT NULL"
 
         if options.key?(:before)
           sql << " AND ts < '#{Conversions.time_to_utc_string(options[:before])}'"