diff --git a/activerecord/lib/active_record/type/serialized.rb b/activerecord/lib/active_record/type/serialized.rb
index a34b2fe702..2e4d2e0bf8 100644
--- a/activerecord/lib/active_record/type/serialized.rb
+++ b/activerecord/lib/active_record/type/serialized.rb
@@ -61,9 +61,12 @@ module ActiveRecord
         end
 
         def encoded(value)
-          unless default_value?(value)
-            coder.dump(value)
+          return if default_value?(value)
+          payload = coder.dump(value)
+          if payload && binary?
+            payload.force_encoding(Encoding::BINARY)
           end
+          payload
         end
     end
   end
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index a65a919975..19a6661f9e 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -4,6 +4,7 @@ require "cases/helper"
 require "models/person"
 require "models/traffic_light"
 require "models/post"
+require "models/binary_field"
 
 class SerializedAttributeTest < ActiveRecord::TestCase
   fixtures :topics, :posts
@@ -317,6 +318,20 @@ class SerializedAttributeTest < ActiveRecord::TestCase
     assert_equal({}, topic.content)
   end
 
+  if current_adapter?(:Mysql2Adapter)
+    def test_is_not_changed_when_stored_in_mysql_blob
+      value = %w(Fée)
+      model = BinaryField.create!(normal_blob: value, normal_text: value)
+      model.reload
+
+      model.normal_text = value
+      assert_not_predicate model, :normal_text_changed?
+
+      model.normal_blob = value
+      assert_not_predicate model, :normal_blob_changed?
+    end
+  end
+
   def test_values_cast_from_nil_are_persisted_as_nil
     # This is required to fulfil the following contract, which must be universally
     # true in Active Record:
diff --git a/activerecord/test/models/binary_field.rb b/activerecord/test/models/binary_field.rb
new file mode 100644
index 0000000000..9032ae8075
--- /dev/null
+++ b/activerecord/test/models/binary_field.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+class BinaryField < ActiveRecord::Base
+  serialize :normal_blob
+  serialize :normal_text
+end