diff --git a/activerecord/lib/active_record/identity_map.rb b/activerecord/lib/active_record/identity_map.rb
index c0fab27188bb9..57fcfb5110b8b 100644
--- a/activerecord/lib/active_record/identity_map.rb
+++ b/activerecord/lib/active_record/identity_map.rb
@@ -29,15 +29,15 @@ def without
       end
 
       def get(class_name, primary_key)
-        current[[class_name, primary_key]]
+        current[[class_name, primary_key.to_s]]
       end
 
       def add(record)
-        current[[record.class.name, record.id]] = record
+        current[[record.class.name, record.id.to_s]] = record
       end
 
       def remove(record)
-        current.delete([record.class.name, record.id])
+        current.delete([record.class.name, record.id.to_s])
       end
 
       def clear