diff --git a/Gemfile b/Gemfile
index c1aed2d..78342f4 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,7 +15,7 @@ group :development do
   gem "rack-test", "~> 2"
   gem "rake", "~> 13"
   gem "rspec", "~> 3"
-  gem "sinatra", "~> 2"
+  gem "sinatra", "~> 4"
   gem "standardrb", "~> 1"
   gem "vcr", "~> 6"
   gem "webmock", "~> 3"
diff --git a/Gemfile.lock b/Gemfile.lock
index ee7edaf..5e2d155 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -34,8 +34,7 @@ GEM
     language_server-protocol (3.17.0.3)
     lint_roller (1.1.0)
     logger (1.7.0)
-    mustermann (2.0.2)
-      ruby2_keywords (~> 0.0.1)
+    mustermann (3.1.1)
     ostruct (0.6.3)
     parallel (1.26.3)
     parser (3.3.5.0)
@@ -45,9 +44,14 @@ GEM
       stringio
     public_suffix (5.1.1)
     racc (1.8.1)
-    rack (2.2.23)
-    rack-protection (2.2.4)
-      rack
+    rack (3.2.7)
+    rack-protection (4.2.1)
+      base64 (>= 0.1.0)
+      logger (>= 1.6.0)
+      rack (>= 3.0.0, < 4)
+    rack-session (2.1.2)
+      base64 (>= 0.1.0)
+      rack (>= 3.0.0)
     rack-test (2.1.0)
       rack (>= 1.3)
     rainbow (3.1.1)
@@ -88,11 +92,12 @@ GEM
       rubocop (>= 1.48.1, < 2.0)
       rubocop-ast (>= 1.31.1, < 2.0)
     ruby-progressbar (1.13.0)
-    ruby2_keywords (0.0.5)
-    sinatra (2.2.4)
-      mustermann (~> 2.0)
-      rack (~> 2.2)
-      rack-protection (= 2.2.4)
+    sinatra (4.2.1)
+      logger (>= 1.6.0)
+      mustermann (~> 3.0)
+      rack (>= 3.0.0, < 4)
+      rack-protection (= 4.2.1)
+      rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
     standard (1.40.1)
       language_server-protocol (~> 3.17.0.2)
@@ -109,7 +114,7 @@ GEM
     standardrb (1.0.1)
       standard
     stringio (3.1.1)
-    tilt (2.4.0)
+    tilt (2.9.0)
     unicode-display_width (2.6.0)
     vcr (6.3.1)
       base64
@@ -131,7 +136,7 @@ DEPENDENCIES
   rack-test (~> 2)
   rake (~> 13)
   rspec (~> 3)
-  sinatra (~> 2)
+  sinatra (~> 4)
   standardrb (~> 1)
   vcr (~> 6)
   webmock (~> 3)