Address comments

lib/liquid/block_body.rb

@@ -16,11 +16,10 @@ module Liquid
     def initialize
       @nodelist = []
       @blank    = true
-      @frozen   = false
     end
 
     def parse(tokenizer, parse_context, &block)
-      raise FrozenError, "can't modify frozen Liquid::BlockBody" if @frozen
+      raise FrozenError, "can't modify frozen Liquid::BlockBody" if frozen?
 
       parse_context.line_number = tokenizer.line_number
 
@@ -31,8 +30,9 @@ module Liquid
       end
     end
 
-    def freeze(_context)
-      @frozen = true
+    def freeze
+      @nodelist.freeze
+      super
     end
 
     private def parse_for_liquid_tag(tokenizer, parse_context)
@@ -199,7 +199,7 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
-      raise "Can only render when frozen" unless @frozen
+      raise "Can only render when frozen" unless frozen?
 
       context.resource_limits.increment_render_score(@nodelist.length)