diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e9a9ec538..3278673bf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,8 +12,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.6', '2.7', '3.0', '3.1', '3.2' ]
-        os: [ macOS-13 ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4', '4.0' ]
+        os: [ macOS-15 ]
     runs-on: ${{ matrix.os }}
 
     name: Ruby ${{ matrix.ruby }} on ${{ matrix.os }}
@@ -39,7 +39,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.6', '2.7', '3.0', '3.1', '3.2' ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4', '4.0' ]
         os: [ ubuntu-22.04 ]
     runs-on: ${{ matrix.os }}
 
diff --git a/rugged.gemspec b/rugged.gemspec
index 05403f802..a4d35f0a0 100644
--- a/rugged.gemspec
+++ b/rugged.gemspec
@@ -31,5 +31,6 @@ desc
   s.add_development_dependency "rake-compiler", ">= 0.9.0"
   s.add_development_dependency "pry"
   s.add_development_dependency "minitest", "~> 5.0"
+  s.add_development_dependency "base64"
   s.metadata["msys2_mingw_dependencies"] = "libssh2 cmake"
 end