diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index f158d5357d..56013c5f95 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Deprecate `Module#reachable?` method.
+
+    *bogdanvlviv*
+
 *   Add `config/credentials.yml.enc` to store production app secrets.
 
     Allows saving any authentication credentials for third party services
diff --git a/activesupport/lib/active_support/core_ext/module/reachable.rb b/activesupport/lib/active_support/core_ext/module/reachable.rb
index 91b230b46c..790a3cc561 100644
--- a/activesupport/lib/active_support/core_ext/module/reachable.rb
+++ b/activesupport/lib/active_support/core_ext/module/reachable.rb
@@ -7,4 +7,5 @@ class Module
   def reachable? #:nodoc:
     !anonymous? && name.safe_constantize.equal?(self)
   end
+  deprecate :reachable?
 end
diff --git a/activesupport/test/core_ext/module/reachable_test.rb b/activesupport/test/core_ext/module/reachable_test.rb
index a69fc6839e..097a72fa5b 100644
--- a/activesupport/test/core_ext/module/reachable_test.rb
+++ b/activesupport/test/core_ext/module/reachable_test.rb
@@ -5,13 +5,17 @@ require "active_support/core_ext/module/reachable"
 
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module is not reachable" do
-    assert !Module.new.reachable?
-    assert !Class.new.reachable?
+    assert_deprecated do
+      assert !Module.new.reachable?
+      assert !Class.new.reachable?
+    end
   end
 
   test "ordinary named classes or modules are reachable" do
-    assert Kernel.reachable?
-    assert Object.reachable?
+    assert_deprecated do
+      assert Kernel.reachable?
+      assert Object.reachable?
+    end
   end
 
   test "a named class or module whose constant has gone is not reachable" do
@@ -21,8 +25,10 @@ class AnonymousTest < ActiveSupport::TestCase
     self.class.send(:remove_const, :C)
     self.class.send(:remove_const, :M)
 
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert !c.reachable?
+      assert !m.reachable?
+    end
   end
 
   test "a named class or module whose constants store different objects are not reachable" do
@@ -35,9 +41,11 @@ class AnonymousTest < ActiveSupport::TestCase
     eval "class C; end"
     eval "module M; end"
 
-    assert C.reachable?
-    assert M.reachable?
-    assert !c.reachable?
-    assert !m.reachable?
+    assert_deprecated do
+      assert C.reachable?
+      assert M.reachable?
+      assert !c.reachable?
+      assert !m.reachable?
+    end
   end
 end