1 files changed, 10 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index c263edd2c6..97f531d064 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -20,6 +20,10 @@ module ActiveRecord
 
       private
 
+        def find_target?
+          !loaded? && foreign_key_present? && klass
+        end
+
         def update_counters(record)
           counter_cache_name = reflection.counter_cache_column
 
@@ -37,11 +41,15 @@ module ActiveRecord
         # Checks whether record is different to the current target, without loading it
         def different_target?(record)
           record.nil? && owner[reflection.foreign_key] ||
-          record.id   != owner[reflection.foreign_key]
+          record && record.id != owner[reflection.foreign_key]
         end
 
         def replace_keys(record)
-          owner[reflection.foreign_key] = record && record[reflection.association_primary_key]
+          if record
+            owner[reflection.foreign_key] = record[reflection.association_primary_key(record.class)]
+          else
+            owner[reflection.foreign_key] = nil
+          end
         end
 
         def foreign_key_present?