diff --git a/Gemfile b/Gemfile
index 3f8018510..127d5032d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -24,4 +24,5 @@ gem "standard", "~> 1.24"
 gem "paint", "~> 2.3"
 gem "dotenv", "~> 2.8"
 gem "listen", "~> 3.0"
+gem "memoize", "~> 1.3"
 gem "rake"
diff --git a/Gemfile.lock b/Gemfile.lock
index 986bf770b..5d3bc2873 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -65,6 +65,7 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     memo_wise (1.7.0)
+    memoize (1.3.1)
     nanoc (4.12.15)
       addressable (~> 2.5)
       colored (~> 1.2)
@@ -164,6 +165,7 @@ PLATFORMS
 DEPENDENCIES
   dotenv (~> 2.8)
   listen (~> 3.0)
+  memoize (~> 1.3)
   nanoc (~> 4.12)
   nanoc-gzip.rb!
   nanoc-webpack.rb!
diff --git a/nanoc/lib/mixin.rb b/nanoc/lib/mixin.rb
index c021fe155..101d38497 100644
--- a/nanoc/lib/mixin.rb
+++ b/nanoc/lib/mixin.rb
@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
 module Mixin
+  require "memoize"
+  extend Memoize
+
   require_relative "mixin/t"
   require_relative "mixin/inline"
   require_relative "mixin/erb"
@@ -10,6 +13,7 @@ module Mixin
     nanoc = Ryo.from YAML.load_file(File.join(Dir.getwd, "nanoc.yaml"))
     nanoc.output_dir
   end
+  memoize :build_dir
 
   include T
   include Inline
diff --git a/nanoc/lib/mixin/t.rb b/nanoc/lib/mixin/t.rb
index 322bc124b..476d46480 100644
--- a/nanoc/lib/mixin/t.rb
+++ b/nanoc/lib/mixin/t.rb
@@ -1,14 +1,15 @@
 module Mixin::T
+  extend Memoize
+
   def t(locale, key, local_assigns = {})
     str = [locale, *key.split(".")].inject(i18n) { _1[_2] }
     format(str, local_assigns)
   end
 
   def i18n
-    @i18n ||= Ryo.from(
-      JSON.parse(
-        File.read(File.join(Dir.getwd, "src", "i18n.json"))
-      )
-    )
+    path = File.join(Dir.getwd, "src", "i18n.json")
+    json = File.binread(path)
+    Ryo.from JSON.parse(json)
   end
+  memoize :i18n
 end