diff --git a/README.md b/README.md
index b7d2530a..d3be75fc 100644
--- a/README.md
+++ b/README.md
@@ -526,6 +526,7 @@ config.settings['RUN_CI'] # => '1'
   - `.configuration` - settings definitions;
   - `.configure` - configuration;
   - `.config` - config object;
+  - settings definitions can be inherited;
 - instance-level:
   - `#configure` - configuration;
   - `#config` - config object;
diff --git a/lib/qonfig/commands/compose.rb b/lib/qonfig/commands/compose.rb
index 0716938a..13636cd5 100644
--- a/lib/qonfig/commands/compose.rb
+++ b/lib/qonfig/commands/compose.rb
@@ -13,6 +13,8 @@ class Compose < Base
 
       # @param data_set_klass [Qonfig::DataSet]
       #
+      # @raise [Qonfig::ArgumentError]
+      #
       # @api private
       # @since 0.1.0
       def initialize(data_set_klass)
diff --git a/spec/features/composition_spec.rb b/spec/features/composition_spec.rb
index 3f0ca454..ed4555d1 100644
--- a/spec/features/composition_spec.rb
+++ b/spec/features/composition_spec.rb
@@ -173,21 +173,21 @@ class ProjectConfig < Qonfig::DataSet
     AppropriateConfig = Class.new(Qonfig::DataSet)
 
     expect do
-      # (incorrect) on the root
+      # (with incompatible config class) on the root
       Class.new(Qonfig::DataSet) do
         compose InappropriateConfig
       end
     end.to raise_error(Qonfig::ArgumentError)
 
     expect do
-      # (correct) on the root
+      # (with compatible config class) on the root
       Class.new(Qonfig::DataSet) do
         compose AppropriateConfig
       end
     end.not_to raise_error
 
     expect do
-      # (incorrect) nested
+      # (with incompatible config class) nested
       Class.new(Qonfig::DataSet) do
         setting :nested do
           compose InappropriateConfig
@@ -196,7 +196,7 @@ class ProjectConfig < Qonfig::DataSet
     end.to raise_error(Qonfig::ArgumentError)
 
     expect do
-      # (correct) nested
+      # (with compatible config class) nested
       Class.new(Qonfig::DataSet) do
         setting :nested do
           compose AppropriateConfig