diff --git a/lib/locale_file_walker.rb b/lib/locale_file_walker.rb
new file mode 100644
index 00000000000..0ac3146e84e
--- /dev/null
+++ b/lib/locale_file_walker.rb
@@ -0,0 +1,48 @@
+require 'psych'
+
+class LocaleFileWalker
+  protected
+
+  def handle_document(document)
+    # we want to ignore the language (first key), so let's start at -1
+    handle_nodes(document.root.children, -1, [])
+  end
+
+  def handle_nodes(nodes, depth, parents)
+    if nodes
+      consecutive_scalars = 0
+      nodes.each do |node|
+        consecutive_scalars = handle_node(node, depth, parents, consecutive_scalars)
+      end
+    end
+  end
+
+  def handle_node(node, depth, parents, consecutive_scalars)
+    node_is_scalar = node.is_a?(Psych::Nodes::Scalar)
+
+    if node_is_scalar
+      handle_scalar(node, depth, parents) if valid_scalar?(depth, consecutive_scalars)
+    elsif node.is_a?(Psych::Nodes::Alias)
+      handle_alias(node, depth, parents)
+    elsif node.is_a?(Psych::Nodes::Mapping)
+      handle_mapping(node, depth, parents)
+      handle_nodes(node.children, depth + 1, parents.dup)
+    end
+
+    node_is_scalar ? consecutive_scalars + 1 : 0
+  end
+
+  def valid_scalar?(depth, consecutive_scalars)
+    depth >= 0 && consecutive_scalars.even?
+  end
+
+  def handle_scalar(node, depth, parents)
+    parents[depth] = node.value
+  end
+
+  def handle_alias(node, depth, parents)
+  end
+
+  def handle_mapping(node, depth, parents)
+  end
+end
diff --git a/spec/integrity/i18n_spec.rb b/spec/integrity/i18n_spec.rb
index 2525668f542..e7b9c08fec9 100644
--- a/spec/integrity/i18n_spec.rb
+++ b/spec/integrity/i18n_spec.rb
@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'locale_file_walker'
 
 describe "i18n integrity checks" do
 
@@ -57,4 +58,40 @@ describe "i18n integrity checks" do
     end
   end
 
+  describe 'keys in English locale files' do
+    locale_files = ['config/locales', 'plugins/**/locales']
+                     .product(['server.en.yml', 'client.en.yml'])
+                     .collect { |dir, filename| Dir["#{Rails.root}/#{dir}/#{filename}"] }
+                     .flatten
+                     .map { |path| Pathname.new(path).relative_path_from(Rails.root) }
+
+    class DuplicateKeyFinder < LocaleFileWalker
+      def find_duplicates(filename)
+        @keys_with_count = {}
+
+        document = Psych.parse_file(filename)
+        handle_document(document)
+
+        @keys_with_count.delete_if { |key, count| count <= 1 }.keys
+      end
+
+      protected
+
+      def handle_scalar(node, depth, parents)
+        super(node, depth, parents)
+
+        key = parents.join('.')
+        @keys_with_count[key] = @keys_with_count.fetch(key, 0) + 1
+      end
+    end
+
+    locale_files.each do |path|
+      context path do
+        it 'has no duplicate keys' do
+          duplicates = DuplicateKeyFinder.new.find_duplicates("#{Rails.root}/#{path}")
+          expect(duplicates).to be_empty
+        end
+      end
+    end
+  end
 end