diff --git a/lib/xcake.rb b/lib/xcake.rb
index 969f1582..874a2ef7 100644
--- a/lib/xcake.rb
+++ b/lib/xcake.rb
@@ -1,4 +1,3 @@
-require 'xcake/core_ext/array'
 require 'xcake/core_ext/class'
 require 'xcake/core_ext/string'
 
diff --git a/lib/xcake/core_ext/array.rb b/lib/xcake/core_ext/array.rb
deleted file mode 100644
index 2f186248..00000000
--- a/lib/xcake/core_ext/array.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class Array
-  def to_h
-    Hash[*flatten(1)]
-  end
-end
diff --git a/lib/xcake/dependency_provider.rb b/lib/xcake/dependency_provider.rb
index fe150a35..fbe87f8b 100644
--- a/lib/xcake/dependency_provider.rb
+++ b/lib/xcake/dependency_provider.rb
@@ -7,9 +7,9 @@ class DependencyProvider
     def initialize(dependency_class)
       plugins = dependency_class.load_plugins
 
-      @dependency_graph = plugins.map do |p|
-        [p, p.dependencies]
-      end.to_h
+      @dependency_graph = plugins.each_with_object({}) do |p, hash|
+        hash[p] = p.dependencies
+      end
     end
 
     def tsort_each_node(&block)
diff --git a/spec/core_ext/array_spec.rb b/spec/core_ext/array_spec.rb
deleted file mode 100644
index 83d5e2e1..00000000
--- a/spec/core_ext/array_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require 'spec_helper'
-
-describe Array do
-  it 'should convert to hash' do
-    expect(%w(key value).to_h).to eq('key' => 'value')
-  end
-end