diff --git a/.github/workflows/actionlint.yml b/.github/workflows/actionlint.yml
index 53b3ffe..7088027 100644
--- a/.github/workflows/actionlint.yml
+++ b/.github/workflows/actionlint.yml
@@ -51,7 +51,7 @@ jobs:
           echo "number=$pr_number" >> "$GITHUB_OUTPUT"
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - uses: reviewdog/action-actionlint@d290e336d5a743810aef4404f757dc862276d2ae # v1.73.4
+      - uses: reviewdog/action-actionlint@5d802a8ebdcb24d712925118c3a4596f571d8fcd # v1.81.0
         if: ${{ ! steps.pr.outputs.number }}
         with:
           fail_on_error: true
diff --git a/.github/workflows/freeagent-gem.yml b/.github/workflows/freeagent-gem.yml
index 3ceec75..487fc36 100644
--- a/.github/workflows/freeagent-gem.yml
+++ b/.github/workflows/freeagent-gem.yml
@@ -15,7 +15,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
+      - uses: ruby/setup-ruby@7f797815d8adceb1c412e7abefdd1ab4abc47a5f # v1.335.0
         with:
           bundler-cache: true
 
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index cf25a01..76eba85 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -9,7 +9,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
+      - uses: ruby/setup-ruby@7f797815d8adceb1c412e7abefdd1ab4abc47a5f # v1.335.0
         with:
           bundler-cache: true
 
diff --git a/.ruby-version b/.ruby-version
index 4f5e697..7919852 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.5
+4.0.9
diff --git a/Gemfile.lock b/Gemfile.lock
index d204999..2d10012 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -8,7 +8,7 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (8.1.3.1)
+    activesupport (8.1.4.1)
       base64
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.3.1)
@@ -123,7 +123,7 @@ PLATFORMS
   x86_64-linux-gnu
 
 DEPENDENCIES
-  bundler (~> 2.6, >= 2.6.2)
+  bundler (~> 4.0.13)
   guard (~> 2.20.2)
   guard-minitest (~> 3.0.0)
   hermod!
@@ -135,7 +135,7 @@ DEPENDENCIES
   rake (~> 13.2)
 
 CHECKSUMS
-  activesupport (8.1.3.1) sha256=85458765f25ea48b9019c46b6bb3fa5683197bf4280d9f06710a6e8d7a831376
+  activesupport (8.1.4.1) sha256=16ac4f341ca65c85a1fcdb8ac73f68891aae9e3c4a6f9c3a27daed8b00017ed7
   ansi (1.6.0) sha256=ac9ea0c0ea8d32fb4e271348e609963ac78882f34b73836c2a02b3622e666658
   base64 (0.3.0) sha256=27337aeabad6ffae05c265c450490628ef3ebd4b67be58257393227588f5a97b
   bigdecimal (4.1.3) sha256=61ebe1e5e559bdc3cc6f2c0ee7f427321fc838f59611c294356eb04d6e21cf66
diff --git a/hermod.gemspec b/hermod.gemspec
index 9a1a677..b2e1998 100644
--- a/hermod.gemspec
+++ b/hermod.gemspec
@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "libxml-ruby", ">= 5.0.3", "< 6.1.0"
   spec.add_runtime_dependency "activesupport", "> 3.2"
 
-  spec.add_development_dependency "bundler", "~> 2.6", ">= 2.6.2"
+  spec.add_development_dependency "bundler", "~> 4.0.13"
   spec.add_development_dependency "rake", "~> 13.2"
   spec.add_development_dependency "minitest", "~> 6.0"
   spec.add_development_dependency "minitest-reporters", "~> 1.6"