diff --git a/lib/i18n.rb b/lib/i18n.rb
index a30d169a..ba29a1e1 100644
--- a/lib/i18n.rb
+++ b/lib/i18n.rb
@@ -389,7 +389,7 @@ def normalize_key(key, separator)
       @@normalized_key_cache[separator][key] ||=
         case key
         when Array
-          key.map { |k| normalize_key(k, separator) }.flatten
+          key.flat_map { |k| normalize_key(k, separator) }
         else
           keys = key.to_s.split(separator)
           keys.delete('')
diff --git a/lib/i18n/locale/fallbacks.rb b/lib/i18n/locale/fallbacks.rb
index 0a791c65..dee99172 100644
--- a/lib/i18n/locale/fallbacks.rb
+++ b/lib/i18n/locale/fallbacks.rb
@@ -60,7 +60,7 @@ def initialize(*mappings)
       end
 
       def defaults=(defaults)
-        @defaults = defaults.map { |default| compute(default, false) }.flatten
+        @defaults = defaults.flat_map { |default| compute(default, false) }
       end
       attr_reader :defaults
 
@@ -84,13 +84,15 @@ def map(mappings)
       protected
 
       def compute(tags, include_defaults = true, exclude = [])
-        result = Array(tags).collect do |tag|
+        result = Array(tags).flat_map do |tag|
           tags = I18n::Locale::Tag.tag(tag).self_and_parents.map! { |t| t.to_sym } - exclude
           tags.each { |_tag| tags += compute(@map[_tag], false, exclude + tags) if @map[_tag] }
           tags
-        end.flatten
+        end
         result.push(*defaults) if include_defaults
-        result.uniq.compact
+        result.uniq!
+        result.compact!
+        result
       end
     end
   end
diff --git a/lib/i18n/locale/tag/parents.rb b/lib/i18n/locale/tag/parents.rb
index ec53060f..6283e667 100644
--- a/lib/i18n/locale/tag/parents.rb
+++ b/lib/i18n/locale/tag/parents.rb
@@ -3,18 +3,20 @@ module Locale
     module Tag
       module Parents
         def parent
-          @parent ||= begin
-            segs = to_a.compact
-            segs.length > 1 ? self.class.tag(*segs[0..(segs.length-2)].join('-')) : nil
-          end
+          @parent ||=
+            begin
+              segs = to_a
+              segs.compact!
+              segs.length > 1 ? self.class.tag(*segs[0..(segs.length - 2)].join('-')) : nil
+            end
         end
 
         def self_and_parents
-          @self_and_parents ||= [self] + parents
+          @self_and_parents ||= [self].concat parents
         end
 
         def parents
-          @parents ||= ([parent] + (parent ? parent.parents : [])).compact
+          @parents ||= parent ? [parent].concat(parent.parents) : []
         end
       end
     end
diff --git a/lib/i18n/locale/tag/simple.rb b/lib/i18n/locale/tag/simple.rb
index 68642a12..6d9ab565 100644
--- a/lib/i18n/locale/tag/simple.rb
+++ b/lib/i18n/locale/tag/simple.rb
@@ -19,7 +19,7 @@ def initialize(*tag)
         end
 
         def subtags
-          @subtags = tag.to_s.split('-').map { |subtag| subtag.to_s }
+          @subtags = tag.to_s.split('-').map!(&:to_s)
         end
 
         def to_sym