diff --git a/app/logical/tag_name_validator.rb b/app/logical/tag_name_validator.rb
index 63690f9ec..029a8c5c0 100644
--- a/app/logical/tag_name_validator.rb
+++ b/app/logical/tag_name_validator.rb
@@ -1,6 +1,12 @@
 class TagNameValidator < ActiveModel::EachValidator
   def validate_each(record, attribute, value)
-    case Tag.normalize_name(value)
+    value = Tag.normalize_name(value)
+
+    if value.size > 170
+      record.errors.add(attribute, "'#{value}' cannot be more than 255 characters long")
+    end
+
+    case value
     when /\A_*\z/
       record.errors.add(attribute, "'#{value}' cannot be blank")
     when /\*/
diff --git a/test/unit/tag_test.rb b/test/unit/tag_test.rb
index 43a06af12..0c4bd3dce 100644
--- a/test/unit/tag_test.rb
+++ b/test/unit/tag_test.rb
@@ -185,6 +185,7 @@ class TagTest < ActiveSupport::TestCase
       should_not allow_value("café").for(:name).on(:create)
       should_not allow_value("東方").for(:name).on(:create)
       should_not allow_value("FAV:blah").for(:name).on(:create)
+      should_not allow_value("X"*171).for(:name).on(:create)
 
       metatags = PostQueryBuilder::METATAGS + TagCategory.mapping.keys
       metatags.each do |metatag|