diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index d69e5bb485..cb39c8edd0 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Remove deprecated `ActiveSupport::SafeBuffer#prepend`.
+
+    *Rafael Mendonça França*
+
 *   Remove deprecated methods at `Kernel`.
 
     `silence_stderr`, `silence_stream`, `capture` and `quietly`.
diff --git a/activesupport/lib/active_support/core_ext/string/output_safety.rb b/activesupport/lib/active_support/core_ext/string/output_safety.rb
index 231eaedbba..ba8d4acd6d 100644
--- a/activesupport/lib/active_support/core_ext/string/output_safety.rb
+++ b/activesupport/lib/active_support/core_ext/string/output_safety.rb
@@ -1,6 +1,5 @@
 require 'erb'
 require 'active_support/core_ext/kernel/singleton_class'
-require 'active_support/deprecation'
 
 class ERB
   module Util
@@ -190,11 +189,6 @@ module ActiveSupport #:nodoc:
       super(html_escape_interpolated_argument(value))
     end
 
-    def prepend!(value)
-      ActiveSupport::Deprecation.deprecation_warning "ActiveSupport::SafeBuffer#prepend!", :prepend
-      prepend value
-    end
-
     def +(other)
       dup.concat(other)
     end
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index 0af207fae9..cdc695f036 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -667,16 +667,6 @@ class OutputSafetyTest < ActiveSupport::TestCase
     assert_equal other, "&lt;foo&gt;other"
   end
 
-  test "Deprecated #prepend! method is still present" do
-    other = "other".html_safe
-
-    assert_deprecated do
-      other.prepend! "<foo>"
-    end
-
-    assert_equal other, "&lt;foo&gt;other"
-  end
-
   test "Concatting safe onto unsafe yields unsafe" do
     @other_string = "other"