diff --git a/Gemfile.lock b/Gemfile.lock
index 2e58ab79..c374c192 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -14,7 +14,7 @@ PATH
       morpher (~> 0.2.6)
       parser (~> 2.5, >= 2.5.1)
       procto (~> 0.0.2)
-      regexp_parser (~> 1.2)
+      regexp_parser (~> 1.7, >= 1.7.1)
       unparser (~> 0.4.2)
     mutant-rspec (0.8.24)
       mutant (~> 0.8.24)
diff --git a/mutant.gemspec b/mutant.gemspec
index 7f2f3a2b..9fcfb09f 100644
--- a/mutant.gemspec
+++ b/mutant.gemspec
@@ -33,7 +33,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency('morpher',       '~> 0.2.6')
   gem.add_runtime_dependency('parser',        '~> 2.5', '>= 2.5.1')
   gem.add_runtime_dependency('procto',        '~> 0.0.2')
-  gem.add_runtime_dependency('regexp_parser', '~> 1.2')
+  gem.add_runtime_dependency('regexp_parser', '~> 1.7', '>= 1.7.1')
   gem.add_runtime_dependency('unparser',      '~> 0.4.2')
 
   gem.add_development_dependency('parallel', '~> 1.3')
diff --git a/spec/unit/mutant/ast/regexp/parse_spec.rb b/spec/unit/mutant/ast/regexp/parse_spec.rb
index 242dd6fd..a470edee 100644
--- a/spec/unit/mutant/ast/regexp/parse_spec.rb
+++ b/spec/unit/mutant/ast/regexp/parse_spec.rb
@@ -13,11 +13,7 @@ RSpec.describe Mutant::AST::Regexp, '.parse' do
 
   context 'on regexp regexp_parser does not accept' do
     it 'returns nil' do
-      if Regexp::Parser::VERSION >= '1.7.1'
-        expect(apply(/u{/).to_re).to eql(/u{/)
-      else
-        expect(apply(/u{/)).to be(nil)
-      end
+      expect(apply(/u{/).to_re).to eql(/u{/)
     end
   end
 end