diff --git a/lib/trmnl/liquid.rb b/lib/trmnl/liquid.rb
index 859b5de..2f18fc6 100644
--- a/lib/trmnl/liquid.rb
+++ b/lib/trmnl/liquid.rb
@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
 require "liquid"
-require "trmnl/liquid/file_system"
 require "trmnl/liquid/filters"
+require "trmnl/liquid/memory_system"
 require "trmnl/liquid/template_tag"
 
 module TRMNL
   module Liquid
-    def self.build_environment(file_system: TRMNL::Liquid::FileSystem.new, **)
+    def self.build_environment(file_system: TRMNL::Liquid::MemorySystem.new, **)
       ::Liquid::Environment.build(file_system:, **) do |environment|
         environment.register_filter TRMNL::Liquid::Filters
         environment.register_tag "template", TRMNL::Liquid::TemplateTag
diff --git a/lib/trmnl/liquid/file_system.rb b/lib/trmnl/liquid/file_system.rb
deleted file mode 100644
index 472a46c..0000000
--- a/lib/trmnl/liquid/file_system.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-# frozen_string_literal: true
-
-module TRMNL
-  module Liquid
-    # This in-memory "file system" is the backing storage for custom templates
-    # defined {% template [name] %} tags.
-    class FileSystem < ::Liquid::BlankFileSystem
-      def initialize
-        super
-        @templates = {}
-      end
-
-      # called by Markup::LiquidTemplateTag to save users' custom shared templates via our
-      # custom {% template %} tag
-      def register name, body
-        @templates[name] = body
-      end
-
-      # called by ::Liquid::Template for {% render 'foo' %} when rendering screen markup
-      def read_template_file name
-        @templates[name] || fail(::Liquid::FileSystemError, "Template not found: #{name}")
-      end
-    end
-  end
-end
diff --git a/lib/trmnl/liquid/memory_system.rb b/lib/trmnl/liquid/memory_system.rb
new file mode 100644
index 0000000..bfdd946
--- /dev/null
+++ b/lib/trmnl/liquid/memory_system.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module TRMNL
+  module Liquid
+    # An in-memory file system for storing custom templates defined with {% template [name] %} tags.
+    class MemorySystem < ::Liquid::BlankFileSystem
+      def initialize
+        super
+        @templates = {}
+      end
+
+      def register name, body
+        templates[name] = body
+      end
+
+      def read_template_file name
+        templates[name] || fail(::Liquid::FileSystemError, "Template not found: #{name}.")
+      end
+
+      private
+
+      attr_reader :templates
+    end
+  end
+end
diff --git a/spec/trmnl/liquid/template_tag_spec.rb b/spec/trmnl/liquid/template_tag_spec.rb
index 3d7cd05..f40a2eb 100644
--- a/spec/trmnl/liquid/template_tag_spec.rb
+++ b/spec/trmnl/liquid/template_tag_spec.rb
@@ -40,7 +40,7 @@ RSpec.describe TRMNL::Liquid::TemplateTag do
 
     it "answers error for undefined template" do
       content = renderer.call %({% render "bogus" %}), {}
-      expect(content).to eq("Liquid error: Template not found: bogus")
+      expect(content).to eq("Liquid error: Template not found: bogus.")
     end
   end
 end
diff --git a/spec/trmnl/liquid_spec.rb b/spec/trmnl/liquid_spec.rb
index 73681e6..d769276 100644
--- a/spec/trmnl/liquid_spec.rb
+++ b/spec/trmnl/liquid_spec.rb
@@ -6,7 +6,7 @@ RSpec.describe TRMNL::Liquid do
   describe ".build_environment" do
     it "builds with defaults" do
       expect(described_class.build_environment).to have_attributes(
-        file_system: be_a(TRMNL::Liquid::FileSystem),
+        file_system: be_a(TRMNL::Liquid::MemorySystem),
         error_mode: :lax,
         tags: hash_including("template" => TRMNL::Liquid::TemplateTag)
       )