Index: lib/active_record/associations/association_proxy.rb
===================================================================
--- lib/active_record/associations/association_proxy.rb	(revision 2486)
+++ lib/active_record/associations/association_proxy.rb	(revision 5525)
@@ -118,9 +118,13 @@
         end
         
       private
-        def method_missing(method, *args, &block)
+        def method_missing(method, *args)
           if load_target        
-            @target.send(method, *args, &block)
+            if block_given?
+              @target.send(method, *args) { |*block_args| yield(*block_args) }
+            else
+              @target.send(method, *args)
+            end
           end
         end
 
Index: lib/active_record/associations/association_collection.rb
===================================================================
--- lib/active_record/associations/association_collection.rb	(revision 2486)
+++ lib/active_record/associations/association_collection.rb	(revision 5525)
@@ -43,8 +43,12 @@
       end
 
       # Calculate sum using SQL, not Enumerable
-      def sum(*args, &block)
-        calculate(:sum, *args, &block)
+      def sum(*args)
+        if block_given?
+          calculate(:sum, *args) { |*block_args| yield(*block_args) }
+        else
+          calculate(:sum, *args)
+        end
       end
 
       # Remove +records+ from this association.  Does not destroy +records+.
Index: lib/active_record/associations/has_and_belongs_to_many_association.rb
===================================================================
--- lib/active_record/associations/has_and_belongs_to_many_association.rb	(revision 2486)
+++ lib/active_record/associations/has_and_belongs_to_many_association.rb	(revision 5525)
@@ -86,12 +86,20 @@
       alias :concat_with_attributes :push_with_attributes
 
       protected
-        def method_missing(method, *args, &block)
+        def method_missing(method, *args)
           if @target.respond_to?(method) || (!@reflection.klass.respond_to?(method) && Class.respond_to?(method))
-            super
+            if block_given?
+              super { |*block_args| yield(*block_args) }
+            else
+              super
+            end
           else
             @reflection.klass.with_scope(:find => { :conditions => @finder_sql, :joins => @join_sql, :readonly => false }) do
-              @reflection.klass.send(method, *args, &block)
+              if block_given?
+                @reflection.klass.send(method, *args) { |*block_args| yield(*block_args) }
+              else
+                @reflection.klass.send(method, *args)
+              end
             end
           end
         end
Index: lib/active_record/associations/has_many_association.rb
===================================================================
--- lib/active_record/associations/has_many_association.rb	(revision 2486)
+++ lib/active_record/associations/has_many_association.rb	(revision 5525)
@@ -93,9 +93,13 @@
       end
 
       protected
-        def method_missing(method, *args, &block)
+        def method_missing(method, *args)
           if @target.respond_to?(method) || (!@reflection.klass.respond_to?(method) && Class.respond_to?(method))
-            super
+            if block_given?
+              super { |*block_args| yield(*block_args) }
+            else
+              super
+            end
           else
             create_scoping = {}
             set_belongs_to_association_for(create_scoping)
@@ -108,7 +112,11 @@
                 :readonly   => false
               }
             ) do
-              @reflection.klass.send(method, *args, &block)
+              if block_given?
+                @reflection.klass.send(method, *args) { |*block_args| yield(*block_args) }
+              else
+                @reflection.klass.send(method, *args)
+              end
             end
           end
         end
Index: lib/active_record/associations/has_many_through_association.rb
===================================================================
--- lib/active_record/associations/has_many_through_association.rb	(revision 2486)
+++ lib/active_record/associations/has_many_through_association.rb	(revision 5525)
@@ -98,16 +98,30 @@
       end
 
       # Calculate sum using SQL, not Enumerable
-      def sum(*args, &block)
-        calculate(:sum, *args, &block)
+      def sum(*args)
+        if block_given?
+          calculate(:sum, *args) { |*block_args| yield(*block_args) }
+        else
+          calculate(:sum, *args)
+        end
       end
 
       protected
-        def method_missing(method, *args, &block)
+        def method_missing(method, *args)
           if @target.respond_to?(method) || (!@reflection.klass.respond_to?(method) && Class.respond_to?(method))
-            super
+            if block_given?
+              super { |*block_args| yield(*block_args) }
+            else
+              super
+            end
           else
-            @reflection.klass.with_scope(construct_scope) { @reflection.klass.send(method, *args, &block) }
+            @reflection.klass.with_scope(construct_scope) {
+              if block_given?
+                @reflection.klass.send(method, *args) { |*block_args| yield(*block_args) }
+              else
+                @reflection.klass.send(method, *args)
+              end
+            }
           end
         end