thrown ActiveRecord::AssociationTypeMismatch when assigning a wrong value for a namespaced association

fixes #20541

1 files changed, 6 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 930f678ae8..7c729676a7 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -211,9 +211,12 @@ module ActiveRecord
         # the kind of the class of the associated objects. Meant to be used as
         # a sanity check when you are about to assign an associated record.
         def raise_on_type_mismatch!(record)
-          unless record.is_a?(reflection.klass) || record.is_a?(reflection.class_name.constantize)
-            message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
-            raise ActiveRecord::AssociationTypeMismatch, message
+          unless record.is_a?(reflection.klass)
+            fresh_class = reflection.class_name.safe_constantize
+            unless fresh_class && record.is_a?(fresh_class)
+              message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
+              raise ActiveRecord::AssociationTypeMismatch, message
+            end
           end
         end