diff --git a/lib/rouge/lexers/lustre.rb b/lib/rouge/lexers/lustre.rb
index 73701c1093..65cced8998 100644
--- a/lib/rouge/lexers/lustre.rb
+++ b/lib/rouge/lexers/lustre.rb
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*- #
-#
-# adapted from ocaml.rb, hence some ocaml-ism migth remains
+# frozen_string_literal: true
+
 module Rouge
   module Lexers
     class Lustre < RegexLexer
@@ -12,16 +12,16 @@ class Lustre < RegexLexer
 
       def self.keywords
         @keywords ||= Set.new %w(
-          extern unsafe assert const current enum function
-          let node operator returns
-          step struct tel type var  model package needs
-          provides uses is body end include merge
+          extern unsafe assert const current enum function let node operator
+          returns step struct tel type var model package needs provides uses is
+          body end include merge
         )
       end
 
       def self.word_operators
         @word_operators ||= Set.new %w(
-           div and xor mod or not nor if then else fby pre when with) 
+          div and xor mod or not nor if then else fby pre when with
+        )
       end
 
       def self.primitives
@@ -32,8 +32,8 @@ def self.primitives
       id = /[a-z_][\w']*/i
 
       state :root do
-        rule (/\s+/m), Text
-        rule (/false|true/), Keyword::Constant
+        rule %r/\s+/m, Text
+        rule %r/false|true/, Keyword::Constant
         rule %r(\-\-.*), Comment::Single
         rule %r(/\*.*?\*/)m, Comment::Multiline
         rule %r(\(\*.*?\*\))m, Comment::Multiline
@@ -50,31 +50,30 @@ def self.primitives
           end
         end
 
-        rule (/[(){}\[\];]+/), Punctuation
+        rule %r/[(){}\[\];]+/, Punctuation
         rule operator, Operator
 
-        rule (/-?\d[\d_]*(.[\d_]*)?(e[+-]?\d[\d_]*)/i), Num::Float
-        rule (/\d[\d_]*/), Num::Integer
+        rule %r/-?\d[\d_]*(.[\d_]*)?(e[+-]?\d[\d_]*)/i, Num::Float
+        rule %r/\d[\d_]*/, Num::Integer
 
-        rule (/'(?:(\\[\\"'ntbr ])|(\\[0-9]{3})|(\\x\h{2}))'/), Str::Char
-        rule (/'[.]'/), Str::Char
-        rule (/"/), Str::Double, :string
-        rule (/[~?]#{id}/), Name::Variable
+        rule %r/'(?:(\\[\\"'ntbr ])|(\\[0-9]{3})|(\\x\h{2}))'/, Str::Char
+        rule %r/'[.]'/, Str::Char
+        rule %r/"/, Str::Double, :string
+        rule %r/[~?]#{id}/, Name::Variable
       end
 
       state :string do
-        rule (/[^\\"]+/), Str::Double
+        rule %r/[^\\"]+/, Str::Double
         mixin :escape_sequence
-        rule (/\\\n/), Str::Double
-        rule (/"/), Str::Double, :pop!
+        rule %r/\\\n/, Str::Double
+        rule %r/"/, Str::Double, :pop!
       end
 
       state :escape_sequence do
-        rule (/\\[\\"'ntbr]/), Str::Escape
-        rule (/\\\d{3}/), Str::Escape
-        rule (/\\x\h{2}/), Str::Escape
+        rule %r/\\[\\"'ntbr]/, Str::Escape
+        rule %r/\\\d{3}/, Str::Escape
+        rule %r/\\x\h{2}/, Str::Escape
       end
-
     end
   end
 end
diff --git a/spec/lexers/lustre_spec.rb b/spec/lexers/lustre_spec.rb
index caa26228e0..bba0eec25c 100644
--- a/spec/lexers/lustre_spec.rb
+++ b/spec/lexers/lustre_spec.rb
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*- #
+# frozen_string_literal: true
 
 describe Rouge::Lexers::Lustre do
   let(:subject) { Rouge::Lexers::Lustre.new }
@@ -15,4 +16,3 @@
     end
   end
 end
-
diff --git a/spec/visual/samples/lustre b/spec/visual/samples/lustre
index 855c16ef1c..ab3248d08b 100644
--- a/spec/visual/samples/lustre
+++ b/spec/visual/samples/lustre
@@ -2,8 +2,8 @@
 
 -- Constants
 const size = 50; -- size of the sliding windows used to smooth values
-const period = 0.1;  -- in seconds
-const speed_max = 110.0;                                           -- comment with leading whitespace
+const period = 0.1; -- in seconds
+const speed_max = 110.0;    -- comment with leading whitespace
 
 -- Types
 type roof_state = enum { locked, in_motion };