diff --git a/mrbgems/mruby-array-ext/mrblib/array.rb b/mrbgems/mruby-array-ext/mrblib/array.rb
index 5492ba2eb..f3246af4f 100644
--- a/mrbgems/mruby-array-ext/mrblib/array.rb
+++ b/mrbgems/mruby-array-ext/mrblib/array.rb
@@ -686,37 +686,6 @@ class Array
     satisfied ? low : nil
   end
 
-  ##
-  #  call-seq:
-  #     ary.delete_if { |item| block }  -> ary
-  #     ary.delete_if                   -> Enumerator
-  #
-  #  Deletes every element of +self+ for which block evaluates to +true+.
-  #
-  #  The array is changed instantly every time the block is called, not after
-  #  the iteration is over.
-  #
-  #  See also Array#reject!
-  #
-  #  If no block is given, an Enumerator is returned instead.
-  #
-  #     scores = [ 97, 42, 75 ]
-  #     scores.delete_if {|score| score < 80 }   #=> [97]
-
-  def delete_if(&block)
-    return to_enum :delete_if unless block
-
-    idx = 0
-    while idx < self.size do
-      if block.call(self[idx])
-        self.delete_at(idx)
-      else
-        idx += 1
-      end
-    end
-    self
-  end
-
   ##
   #  call-seq:
   #     ary.keep_if { |item| block } -> ary
diff --git a/mrbgems/mruby-array-ext/test/array.rb b/mrbgems/mruby-array-ext/test/array.rb
index 51172f9a8..2955ef391 100644
--- a/mrbgems/mruby-array-ext/test/array.rb
+++ b/mrbgems/mruby-array-ext/test/array.rb
@@ -299,19 +299,6 @@ end
 #assert("Array#bsearch_index") do
 #end
 
-assert("Array#delete_if") do
-  a = [1, 2, 3, 4, 5]
-  assert_equal [1, 2, 3, 4, 5], a.delete_if { false }
-  assert_equal [1, 2, 3, 4, 5], a
-
-  a = [1, 2, 3, 4, 5]
-  assert_equal [], a.delete_if { true }
-  assert_equal [], a
-
-  a = [ 1, 2, 3, 4, 5 ]
-  assert_equal [1, 2, 3], a.delete_if { |val| val > 3 }
-end
-
 assert("Array#keep_if") do
   a = [1, 2, 3, 4, 5]
   assert_equal [1, 2, 3, 4, 5], a.keep_if { true }