diff --git a/activerecord/lib/active_record/attribute_set/builder.rb b/activerecord/lib/active_record/attribute_set/builder.rb
index 4134032659ed28b0e4d439cb12ded9a72cda9422..73b77d2edad79144eb95b0334e8cabbb86264b45 100644
--- a/activerecord/lib/active_record/attribute_set/builder.rb
+++ b/activerecord/lib/active_record/attribute_set/builder.rb
@@ -23,7 +23,6 @@ def build_from_database(values = {}, additional_types = {})
 
   class LazyAttributeHash
     delegate :select, :transform_values, to: :materialize
-    delegate :[]=, :freeze, to: :delegate_hash
 
     def initialize(types, values, additional_types)
       @types = types
@@ -45,6 +44,13 @@ def [](key)
       end
     end
 
+    def []=(key, value)
+      if frozen?
+        raise RuntimeError, "Can't modify frozen hash"
+      end
+      delegate_hash[key] = value
+    end
+
     def initialized_keys
       delegate_hash.keys | values.keys
     end
@@ -54,11 +60,6 @@ def initialize_dup(_)
       super
     end
 
-    def initialize_clone(_)
-      @delegate_hash = delegate_hash.clone
-      super
-    end
-
     protected
 
     attr_reader :types, :values, :additional_types, :delegate_hash