diff --git a/Gemfile b/Gemfile
index 240eff6..b15d01f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -20,16 +20,16 @@ gem "multi_json", "~> 1.15"
 gem "oauth2", "~> 2.0"
 gem "pg", "~> 1.5"
 gem "puma", "~> 6.4"
-gem "rack", "~> 2.2"
+gem "rack", "~> 3.0"
 gem "rack-attack", "~> 6.7.0"
 gem "rack-test", "~> 2.1"
 gem "rake", "~> 13.1"
 gem "redis", "~> 5.1.0"
 gem "rspec", "~> 3.12"
 gem "sentry-ruby", "~> 5.16"
-gem "sinatra", "~> 3.2"
+gem "sinatra", "~> 4.0"
 gem "sinatra-activerecord", "~> 2.0.27"
-gem "sinatra-contrib", "~> 3.2"
+gem "sinatra-contrib", "~> 4.0"
 gem "sinatra-cross_origin", "~> 0.4.0"
 gem "unleash", "~> 5.0"
 gem "uuid", "~> 2.3"
diff --git a/Gemfile.lock b/Gemfile.lock
index b9d450f..ca4dc4a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -77,12 +77,14 @@ GEM
     puma (6.4.2)
       nio4r (~> 2.0)
     racc (1.7.3)
-    rack (2.2.8.1)
+    rack (3.0.9.1)
     rack-attack (6.7.0)
       rack (>= 1.0, < 4)
-    rack-protection (3.2.0)
+    rack-protection (4.0.0)
       base64 (>= 0.1.0)
-      rack (~> 2.2, >= 2.2.4)
+      rack (>= 3.0.0, < 4)
+    rack-session (2.0.0)
+      rack (>= 3.0.0)
     rack-test (2.1.0)
       rack (>= 1.3)
     rainbow (3.1.1)
@@ -147,19 +149,20 @@ GEM
     ruby2_keywords (0.0.5)
     sentry-ruby (5.16.1)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-    sinatra (3.2.0)
+    sinatra (4.0.0)
       mustermann (~> 3.0)
-      rack (~> 2.2, >= 2.2.4)
-      rack-protection (= 3.2.0)
+      rack (>= 3.0.0, < 4)
+      rack-protection (= 4.0.0)
+      rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
     sinatra-activerecord (2.0.27)
       activerecord (>= 4.1)
       sinatra (>= 1.0)
-    sinatra-contrib (3.2.0)
+    sinatra-contrib (4.0.0)
       multi_json (>= 0.0.2)
       mustermann (~> 3.0)
-      rack-protection (= 3.2.0)
-      sinatra (= 3.2.0)
+      rack-protection (= 4.0.0)
+      sinatra (= 4.0.0)
       tilt (~> 2.0)
     sinatra-cross_origin (0.4.0)
     snaky_hash (2.0.1)
@@ -196,7 +199,7 @@ DEPENDENCIES
   oauth2 (~> 2.0)
   pg (~> 1.5)
   puma (~> 6.4)
-  rack (~> 2.2)
+  rack (~> 3.0)
   rack-attack (~> 6.7.0)
   rack-test (~> 2.1)
   rake (~> 13.1)
@@ -205,9 +208,9 @@ DEPENDENCIES
   rubocop-govuk (~> 4.13)
   rubocop-performance (~> 1.20)
   sentry-ruby (~> 5.16)
-  sinatra (~> 3.2)
+  sinatra (~> 4.0)
   sinatra-activerecord (~> 2.0.27)
-  sinatra-contrib (~> 3.2)
+  sinatra-contrib (~> 4.0)
   sinatra-cross_origin (~> 0.4.0)
   timecop
   unleash (~> 5.0)