1 files changed, 5 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 5d91315aad..d7aa4bfa98 100755
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1268,7 +1268,11 @@ module ActiveRecord
 
           if association_proxy_class == BelongsToAssociation
             define_method("#{reflection.primary_key_name}=") do |target_id|
-              instance_variable_get(ivar).reset if instance_variable_defined?(ivar)
+              if instance_variable_defined?(ivar)
+                if association = instance_variable_get(ivar)
+                  association.reset
+                end
+              end
               write_attribute(reflection.primary_key_name, target_id)
             end
           end