diff --git a/mutant.gemspec b/mutant.gemspec
index 22af8591..2f528f84 100644
--- a/mutant.gemspec
+++ b/mutant.gemspec
@@ -21,7 +21,7 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version = '>= 2.1'
 
-  gem.add_runtime_dependency('parser',        '~> 2.3.0', '>= 2.3.0.2')
+  gem.add_runtime_dependency('parser',        '= 2.3.1.2')
   gem.add_runtime_dependency('ast',           '~> 2.2')
   gem.add_runtime_dependency('diff-lcs',      '~> 1.2')
   gem.add_runtime_dependency('parallel',      '~> 1.3')
@@ -37,7 +37,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency('concord',       '~> 0.1.5')
   gem.add_runtime_dependency('regexp_parser', '~> 0.3.6')
 
-  gem.add_development_dependency('devtools', '~> 0.1.4')
+  gem.add_development_dependency('devtools', '= 0.1.10')
   gem.add_development_dependency('bundler',  '~> 1.10')
   gem.add_development_dependency('ffi',      '~> 1.9.6')
 end
diff --git a/spec/unit/mutant/ast/regexp_spec.rb b/spec/unit/mutant/ast/regexp_spec.rb
index 7d6c1f7b..eb987953 100644
--- a/spec/unit/mutant/ast/regexp_spec.rb
+++ b/spec/unit/mutant/ast/regexp_spec.rb
@@ -70,9 +70,9 @@ module RegexpSpec
 
         include_context 'regexp transformation'
 
-        return if regexp.encoding.name.eql?('ASCII-8BIT')
-
-        include_context 'regexp round trip'
+        unless regexp.encoding.name.eql?('ASCII-8BIT')
+          include_context 'regexp round trip'
+        end
       end
     end
   end