diff --git a/.rubocop.yml b/.rubocop.yml
index 290e51f..0fd1fdb 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -6,6 +6,8 @@ AllCops:
   TargetRubyVersion:  2.3
   Exclude:
     - lib/tasks/*.rake
+    - vendor/**/*
+    - tmp/**/*
 
 Bundler/DuplicatedGem:
   Enabled: false
@@ -36,6 +38,9 @@ Style/Lambda:
 Style/LambdaCall:
   Enabled: false
 
+Style/ModuleFunction:
+  Enabled: false
+
 Style/RescueModifier:
   Exclude:
     - spec/**/*.rb
diff --git a/.travis.yml b/.travis.yml
index e4365d9..ca20c0a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,8 @@ language: ruby
 cache: bundler
 bundler_args: --without benchmarks tools
 script:
-  - bundle exec rake spec
+  - bundle exec rspec
+  - bundle exec rubocop
 rvm:
   - 2.3.8
   - 2.4.6
@@ -11,7 +12,6 @@ rvm:
   - 2.6.3
   - jruby-9.2.7.0
   - jruby-9000
-  - rbx-3
   - ruby-head
   - truffleruby
 env:
@@ -19,7 +19,6 @@ env:
     - JRUBY_OPTS='--dev -J-Xmx1024M'
 matrix:
   allow_failures:
-    - rvm: rbx-3
     - rvm: ruby-head
     - rvm: jruby-head
     - rvm: truffleruby
diff --git a/lib/dry/initializer/config.rb b/lib/dry/initializer/config.rb
index 1000b9e..903e28e 100644
--- a/lib/dry/initializer/config.rb
+++ b/lib/dry/initializer/config.rb
@@ -142,7 +142,7 @@ def add_definition(option, name, type, block, **opts)
         source: name,
         type:   type,
         block:  block,
-        **opts,
+        **opts
       }
 
       options = Dispatchers.call(opts)
diff --git a/lib/dry/initializer/struct.rb b/lib/dry/initializer/struct.rb
index ab794b2..9d84673 100644
--- a/lib/dry/initializer/struct.rb
+++ b/lib/dry/initializer/struct.rb
@@ -8,7 +8,7 @@ class << self
     undef_method :param
 
     def new(options)
-      super Hash(options).transform_keys(&:to_sym)
+      super Hash(options).each_with_object({}) { |(k, v), h| h[k.to_sym] = v }
     end
     alias call new
   end
@@ -22,8 +22,7 @@ def to_h
       .class
       .dry_initializer
       .attributes(self)
-      .transform_values { |v| __hashify(v) }
-      .stringify_keys
+      .each_with_object({}) { |(k, v), h| h[k.to_s] = __hashify(v) }
   end
 
   private
diff --git a/spec/nested_type_spec.rb b/spec/nested_type_spec.rb
index 1256dd3..db43431 100644
--- a/spec/nested_type_spec.rb
+++ b/spec/nested_type_spec.rb
@@ -18,6 +18,10 @@ class Test::Xyz
     it "builds the type" do
       expect(subject.x.y.z).to eq "42"
     end
+
+    it "converts the nested type to hash" do
+      expect(subject.x.to_h).to eq("y" => { "z" => "42" })
+    end
   end
 
   context "with nested and wrapped definitions" do
diff --git a/spec/type_argument_spec.rb b/spec/type_argument_spec.rb
index 69912b5..c78cbce 100644
--- a/spec/type_argument_spec.rb
+++ b/spec/type_argument_spec.rb
@@ -13,7 +13,7 @@ class Test::Foo
     subject { Test::Foo.new 1, bar: "2" }
 
     it "raises TypeError" do
-      expect { subject }.to raise_error TypeError, /1/
+      expect { subject }.to raise_error Dry::Types::ConstraintError, /1/
     end
   end
 
@@ -21,7 +21,7 @@ class Test::Foo
     subject { Test::Foo.new "1", bar: 2 }
 
     it "raises TypeError" do
-      expect { subject }.to raise_error TypeError, /2/
+      expect { subject }.to raise_error Dry::Types::ConstraintError, /2/
     end
   end
 
diff --git a/spec/type_constraint_spec.rb b/spec/type_constraint_spec.rb
index 86f4364..9f2b40d 100644
--- a/spec/type_constraint_spec.rb
+++ b/spec/type_constraint_spec.rb
@@ -43,7 +43,7 @@ class Test::Foo
       subject { Test::Foo.new 1 }
 
       it "raises ArgumentError" do
-        expect { subject }.to raise_error TypeError, /1/
+        expect { subject }.to raise_error Dry::Types::ConstraintError, /1/
       end
     end
 
diff --git a/spec/value_coercion_via_dry_types_spec.rb b/spec/value_coercion_via_dry_types_spec.rb
index 20ee1b5..a963119 100644
--- a/spec/value_coercion_via_dry_types_spec.rb
+++ b/spec/value_coercion_via_dry_types_spec.rb
@@ -3,7 +3,7 @@
 describe "value coercion via dry-types" do
   before do
     module Test::Types
-      include Dry::Types.module
+      include Dry.Types
     end
 
     class Test::Foo