diff --git a/CHANGELOG.md b/CHANGELOG.md
index 76a5750..2c6fd4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # CHANGELOG
 
+## v0.12.2 (2026-02-07)
+
+- Drop usage of `String#mb_chars` because of deprecation on ActiveSupport side
+
+## v0.12.1 (2026-01-06)
+
+- Allow to use Sinatra v4, Thin v2 and ActiveSupport v8
+
 ## v0.12.0 (2025-02-07)
 
 - Add basic support for SVG files (Epuber will correctly find them even when extension is missing) [#66](https://github.com/epuber-io/epuber/issues/66)
diff --git a/lib/epuber/book/contributor.rb b/lib/epuber/book/contributor.rb
index b3c17a9..d8fa521 100644
--- a/lib/epuber/book/contributor.rb
+++ b/lib/epuber/book/contributor.rb
@@ -86,7 +86,7 @@ def pretty_name
       # @return [String]
       #
       def file_as
-        "#{@last_name.mb_chars.upcase}, #{@first_name}"
+        "#{@last_name.upcase}, #{@first_name}"
       end
     end
   end
diff --git a/lib/epuber/from_file/bookspec_generator.rb b/lib/epuber/from_file/bookspec_generator.rb
index 818feba..a73807e 100644
--- a/lib/epuber/from_file/bookspec_generator.rb
+++ b/lib/epuber/from_file/bookspec_generator.rb
@@ -284,7 +284,7 @@ def decrease_indent
     # @return [Boolean]
     #
     def contributor_file_as_eq?(file_as_a, file_as_b)
-      file_as_a == file_as_b || file_as_a.mb_chars.downcase == file_as_b.mb_chars.downcase
+      file_as_a == file_as_b || file_as_a.downcase == file_as_b.downcase
     end
 
     # @param [String] href
diff --git a/spec/unit/book/contributor_spec.rb b/spec/unit/book/contributor_spec.rb
index 132eea0..ecbf4d4 100644
--- a/spec/unit/book/contributor_spec.rb
+++ b/spec/unit/book/contributor_spec.rb
@@ -6,41 +6,36 @@
 module Epuber
   class Book
     describe Contributor do
-      before do
-        @contributor = described_class.new('Jason Fried', 'FRIED, Jason', 'aut')
-      end
-
       it 'returns same values' do
-        expect(@contributor.pretty_name).to eq 'Jason Fried'
-        expect(@contributor.file_as).to eq 'FRIED, Jason'
-        expect(@contributor.role).to eq 'aut'
+        contributor = described_class.new('Jason Fried', 'FRIED, Jason', 'aut')
+
+        expect(contributor.pretty_name).to eq 'Jason Fried'
+        expect(contributor.file_as).to eq 'FRIED, Jason'
+        expect(contributor.role).to eq 'aut'
       end
     end
 
     describe NormalContributor do
-      before do
-        @contributor = described_class.new('Jason', 'Fried', 'aut')
-      end
-
-      it 'formats file_as' do
-        expect(@contributor.file_as).to eq 'FRIED, Jason'
-      end
+      it 'automatically formats file_as and pretty_name' do
+        contributor = described_class.new('Jason', 'Fried', 'aut')
 
-      it 'formats pretty_name' do
-        expect(@contributor.pretty_name).to eq 'Jason Fried'
-      end
-
-      it 'pretty_name is readonly' do
+        expect(contributor.file_as).to eq 'FRIED, Jason'
+        expect(contributor.pretty_name).to eq 'Jason Fried'
         expect do
-          @contributor.pretty_name = ''
+          contributor.pretty_name = ''
         end.to raise_error NameError
-      end
 
-      it 'file_as is readonly' do
         expect do
-          @contributor.file_as = ''
+          contributor.file_as = ''
         end.to raise_error NameError
       end
+
+      it 'automatically formats file_as and pretty_name with unicode characters' do
+        contributor = described_class.new('Ěščřžýáíé', 'Úůňó', 'aut')
+
+        expect(contributor.file_as).to eq 'ÚŮŇÓ, Ěščřžýáíé'
+        expect(contributor.pretty_name).to eq 'Ěščřžýáíé Úůňó'
+      end
     end
 
     describe 'Epuber::Contributor.from_obj' do