diff --git a/lib/statsd/instrument/datagram.rb b/lib/statsd/instrument/datagram.rb
index b6151a71..61d66dc5 100644
--- a/lib/statsd/instrument/datagram.rb
+++ b/lib/statsd/instrument/datagram.rb
@@ -77,7 +77,7 @@ def eql?(other)
         (?:\|\#(?<tags>(?:[^\|,]+(?:,[^\|,]+)*)))?
         \n? # In some implementations, the datagram may include a trailing newline.
         \z
-      }x
+      }x.freeze
 
       def parsed_datagram
         @parsed ||= if (match_info = PARSER.match(@source))
diff --git a/lib/statsd/instrument/dogstatsd_datagram.rb b/lib/statsd/instrument/dogstatsd_datagram.rb
index e1b00056..abb4d3f6 100644
--- a/lib/statsd/instrument/dogstatsd_datagram.rb
+++ b/lib/statsd/instrument/dogstatsd_datagram.rb
@@ -69,7 +69,7 @@ def parsed_datagram
         (?:\|m:(?<message>[^\|]+))?
         \n? # In some implementations, the datagram may include a trailing newline.
         \z
-      }x
+      }x.freeze
 
       # |k:my-key|p:low|s:source|t:success|
       EVENT_PARSER = %r{
@@ -84,7 +84,7 @@ def parsed_datagram
         (?:\|\#(?<tags>(?:[^\|,]+(?:,[^\|,]+)*)))?
         \n? # In some implementations, the datagram may include a trailing newline.
         \z
-      }x
+      }x.freeze
 
       PARSER = Regexp.union(StatsD::Instrument::Datagram::PARSER, SERVICE_CHECK_PARSER, EVENT_PARSER)
     end
diff --git a/lib/statsd/instrument/rubocop.rb b/lib/statsd/instrument/rubocop.rb
index 66ca862d..90f796e7 100644
--- a/lib/statsd/instrument/rubocop.rb
+++ b/lib/statsd/instrument/rubocop.rb
@@ -3,7 +3,7 @@
 module RuboCop
   module Cop
     module StatsD
-      METRIC_METHODS = [:increment, :gauge, :measure, :set, :histogram, :distribution, :key_value]
+      METRIC_METHODS = [:increment, :gauge, :measure, :set, :histogram, :distribution, :key_value].freeze
 
       METAPROGRAMMING_METHODS = [
         :statsd_measure,
@@ -11,7 +11,7 @@ module StatsD
         :statsd_count_success,
         :statsd_count_if,
         :statsd_count,
-      ]
+      ].freeze
 
       SINGLETON_CONFIGURATION_METHODS = [
         :backend,
@@ -22,7 +22,7 @@ module StatsD
         :"default_tags=",
         :default_sample_rate,
         :"default_sample_rate=",
-      ]
+      ].freeze
 
       private
 
diff --git a/lib/statsd/instrument/rubocop/metric_return_value.rb b/lib/statsd/instrument/rubocop/metric_return_value.rb
index f1f962c6..6627675c 100644
--- a/lib/statsd/instrument/rubocop/metric_return_value.rb
+++ b/lib/statsd/instrument/rubocop/metric_return_value.rb
@@ -19,7 +19,7 @@ class MetricReturnValue < Base
 
         MSG = "Do not use the return value of StatsD metric methods"
 
-        INVALID_PARENTS = [:lvasgn, :array, :pair, :send, :return, :yield]
+        INVALID_PARENTS = [:lvasgn, :array, :pair, :send, :return, :yield].freeze
 
         def on_send(node)
           if metric_method?(node) && node.arguments.last&.type != :block_pass
diff --git a/test/rubocop/singleton_configuration_test.rb b/test/rubocop/singleton_configuration_test.rb
index 54a92d25..2a640d43 100644
--- a/test/rubocop/singleton_configuration_test.rb
+++ b/test/rubocop/singleton_configuration_test.rb
@@ -18,7 +18,10 @@ def test_offense_statsd_backend
 
     def test_offense_statsd_prefix
       assert_offense('StatsD.prefix = "foo"')
+      # The interpolation is intentionally literal source passed to the cop under test.
+      # rubocop:disable Lint/InterpolationCheck
       assert_offense('"#{StatsD.prefix}.foo"')
+      # rubocop:enable Lint/InterpolationCheck
     end
 
     def test_offense_statsd_default_tags