diff --git a/lib/scout_apm/auto_instrument/layer.rb b/lib/scout_apm/auto_instrument/layer.rb
index 46c51c0b..edc91a68 100644
--- a/lib/scout_apm/auto_instrument/layer.rb
+++ b/lib/scout_apm/auto_instrument/layer.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 
 module ScoutApm
   def self.AutoInstrument(name, backtrace)
diff --git a/lib/scout_apm/tracked_request.rb b/lib/scout_apm/tracked_request.rb
index 3ea7202c..758b7e9a 100644
--- a/lib/scout_apm/tracked_request.rb
+++ b/lib/scout_apm/tracked_request.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+#
 # A TrackedRequest is a stack of layers, where completed layers (go into, then
 # come out of a layer) are forgotten as they finish. Layers are attached to
 # their children as the process goes, building a tree structure within the