diff --git a/Gemfile.lock b/Gemfile.lock
index 7007b90..43b7df1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,79 +1,65 @@
 PATH
   remote: .
   specs:
-    mixture (0.6.2)
+    mixture (0.7.1)
       thread_safe (~> 0.3)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    ast (2.0.0)
-    astrolabe (1.3.0)
-      parser (>= 2.2.0.pre.3, < 3.0)
-    coderay (1.1.0)
-    coveralls (0.8.2)
-      json (~> 1.8)
-      rest-client (>= 1.6.8, < 2)
-      simplecov (~> 0.10.0)
+    ast (2.3.0)
+    coderay (1.1.1)
+    coveralls (0.8.19)
+      json (>= 1.8, < 3)
+      simplecov (~> 0.12.0)
       term-ansicolor (~> 1.3)
       thor (~> 0.19.1)
-    diff-lcs (1.2.5)
+      tins (~> 1.6)
+    diff-lcs (1.3)
     docile (1.1.5)
-    domain_name (0.5.24)
-      unf (>= 0.0.5, < 1.0.0)
-    http-cookie (1.0.2)
-      domain_name (~> 0.5)
-    json (1.8.3)
+    json (2.0.3)
     method_source (0.8.2)
-    mime-types (2.6.1)
-    netrc (0.10.3)
-    parser (2.2.2.6)
-      ast (>= 1.1, < 3.0)
+    parser (2.4.0.0)
+      ast (~> 2.2)
     powerpack (0.1.1)
-    pry (0.10.1)
+    pry (0.10.4)
       coderay (~> 1.1.0)
       method_source (~> 0.8.1)
       slop (~> 3.4)
-    rainbow (2.0.0)
-    rake (10.4.2)
-    rest-client (1.8.0)
-      http-cookie (>= 1.0.2, < 2.0)
-      mime-types (>= 1.16, < 3.0)
-      netrc (~> 0.7)
-    rspec (3.3.0)
-      rspec-core (~> 3.3.0)
-      rspec-expectations (~> 3.3.0)
-      rspec-mocks (~> 3.3.0)
-    rspec-core (3.3.1)
-      rspec-support (~> 3.3.0)
-    rspec-expectations (3.3.0)
+    rainbow (2.2.1)
+    rake (12.0.0)
+    rspec (3.5.0)
+      rspec-core (~> 3.5.0)
+      rspec-expectations (~> 3.5.0)
+      rspec-mocks (~> 3.5.0)
+    rspec-core (3.5.4)
+      rspec-support (~> 3.5.0)
+    rspec-expectations (3.5.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.3.0)
-    rspec-mocks (3.3.1)
+      rspec-support (~> 3.5.0)
+    rspec-mocks (3.5.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.3.0)
-    rspec-support (3.3.0)
-    rubocop (0.32.1)
-      astrolabe (~> 1.3)
-      parser (>= 2.2.2.5, < 3.0)
+      rspec-support (~> 3.5.0)
+    rspec-support (3.5.0)
+    rubocop (0.47.1)
+      parser (>= 2.3.3.1, < 3.0)
       powerpack (~> 0.1)
       rainbow (>= 1.99.1, < 3.0)
-      ruby-progressbar (~> 1.4)
-    ruby-progressbar (1.7.5)
-    simplecov (0.10.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (~> 1.0, >= 1.0.1)
+    ruby-progressbar (1.8.1)
+    simplecov (0.12.0)
       docile (~> 1.1.0)
-      json (~> 1.8)
+      json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.0)
     slop (3.6.0)
-    term-ansicolor (1.3.2)
+    term-ansicolor (1.4.0)
       tins (~> 1.0)
-    thor (0.19.1)
-    thread_safe (0.3.5)
-    tins (1.5.4)
-    unf (0.1.4)
-      unf_ext
-    unf_ext (0.0.7.1)
+    thor (0.19.4)
+    thread_safe (0.3.6)
+    tins (1.13.2)
+    unicode-display_width (1.1.3)
 
 PLATFORMS
   ruby
@@ -88,4 +74,4 @@ DEPENDENCIES
   rubocop
 
 BUNDLED WITH
-   1.10.6
+   1.13.6
diff --git a/lib/mixture/extensions/attributable.rb b/lib/mixture/extensions/attributable.rb
index 5782d61..52826f7 100644
--- a/lib/mixture/extensions/attributable.rb
+++ b/lib/mixture/extensions/attributable.rb
@@ -29,12 +29,17 @@ def attribute(name, options = {})
         # @see AttributeList
         # @return [AttributeList]
         def attributes
-          return @_attributes if @_attributes
+          @_attributes ||= build_attributes
+        end
+
+      private
+
+        def build_attributes
           available = ancestors[1..-1]
                       .select { |c| c.respond_to?(:attributes) }
                       .first
           parent = available ? available.attributes : nil
-          @_attributes = AttributeList.new(parent)
+          AttributeList.new(parent)
         end
       end
 
@@ -66,7 +71,7 @@ def attributes
         # @param attr [Symbol] The attribute.
         # @raise [ArgumentError]
         def unknown_attribute(attr)
-          fail ArgumentError, "Unknown attribute #{attr} passed"
+          fail ArgumentError, "Unknown attribute #{attr.inspect} passed"
         end
 
         # @overload attribute(key)
diff --git a/lib/mixture/version.rb b/lib/mixture/version.rb
index 31e2ec0..c549090 100644
--- a/lib/mixture/version.rb
+++ b/lib/mixture/version.rb
@@ -6,5 +6,5 @@ module Mixture
   # The current version of Mixture.
   #
   # @return [String]
-  VERSION = "0.7.0"
+  VERSION = "0.7.1"
 end