diff --git a/lib/mongoid_nested_set/base.rb b/lib/mongoid_nested_set/base.rb
index 57e43d9..4ce7eda 100644
--- a/lib/mongoid_nested_set/base.rb
+++ b/lib/mongoid_nested_set/base.rb
@@ -53,7 +53,11 @@ def acts_as_nested_set(options = {})
 
         attr_accessor :skip_before_destroy
 
-        if accessible_attributes.blank?
+        # Rails 4 no longer uses "attr_protected" and "attr_accessible" for
+        # mass assignment control by default, but this methods can be restored 
+        # by installing 'protected_attributes' gem. So here we just check
+        # accessible_attributes method presence
+        if respond_to?(:accessible_attributes) && accessible_attributes.blank?
           attr_protected left_field_name.intern, right_field_name.intern
         end
 
diff --git a/lib/mongoid_nested_set/update.rb b/lib/mongoid_nested_set/update.rb
index 12d688a..0b8916f 100755
--- a/lib/mongoid_nested_set/update.rb
+++ b/lib/mongoid_nested_set/update.rb
@@ -153,7 +153,7 @@ def move_to(target, position)
           ).update_all("$inc" => { right_field_name => -width })
         end
 
-        self.set(parent_field_name, new_parent)
+        self.mongoid_set(parent_field_name, new_parent)
         self.reload_nested_set
         self.update_self_and_descendants_depth
 
@@ -188,7 +188,7 @@ def update_depth
     def update_self_and_descendants_depth
       if depth?
         scope_class.each_with_level(self_and_descendants) do |node, level|
-          node.with(:safe => true).set(:depth, level) unless node.depth == level
+          node.with(:safe => true).mongoid_set(:depth, level) unless node.depth == level
         end
         self.reload
       end
@@ -214,17 +214,37 @@ def destroy_descendants
       # update lefts and rights for remaining nodes
       diff = right - left + 1
 
-      scope_class.with(:safe => true).where(
+      c = scope_class.with(:safe => true).where(
         nested_set_scope.where(left_field_name.to_sym.gt => right).selector
-      ).inc(left_field_name, -diff)
+      )
+      mongoid_inc(c, left_field_name, -diff)
 
-      scope_class.with(:safe => true).where(
+      c = scope_class.with(:safe => true).where(
         nested_set_scope.where(right_field_name.to_sym.gt => right).selector
-      ).inc(right_field_name, -diff)
+      )
+      mongoid_inc(c, right_field_name, -diff)
 
       # Don't allow multiple calls to destroy to corrupt the set
       self.skip_before_destroy = true
     end
 
+    # Compatibility wrapper for mongoid set method, should works with 3.x.x and
+    # 4.x.x versions
+    def mongoid_set(field, value)
+      if method(:set).arity == 1
+        set({field => value})
+      else
+        set(field, value)
+      end
+    end
+
+    def mongoid_inc(criteria, field, value)
+      if criteria.method(:inc).arity == 2
+        criteria.inc(field, value)        
+      else
+        criteria.inc({field => value})
+      end
+    end
+
   end
 end