diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e57f5204..848db60c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -7,10 +7,11 @@ on:
 
 jobs:
   rspec:
-    timeout-minutes: 10
+    timeout-minutes: 15
     runs-on: ${{ matrix.os }}-latest
 
     strategy:
+      fail-fast: false
       matrix:
         ruby-version:
           - '2.6'
@@ -19,6 +20,13 @@ jobs:
           - '3.1'
         os:
           - ubuntu
+          - windows
+
+        # Tempfile behavior has changed on Ruby 3.1 such that tests
+        # fail with permission denied. Would welcome a PR with a fix.
+        exclude:
+          - ruby-version: '3.1'
+            os: windows
 
     steps:
       - uses: actions/checkout@v2
diff --git a/lib/overcommit/subprocess.rb b/lib/overcommit/subprocess.rb
index 3be06388..5899274f 100644
--- a/lib/overcommit/subprocess.rb
+++ b/lib/overcommit/subprocess.rb
@@ -2,6 +2,7 @@
 
 require 'childprocess'
 require 'tempfile'
+require 'overcommit/os'
 
 module Overcommit
   # Manages execution of a child process, collecting the exit status and
@@ -91,6 +92,10 @@ def win32_prepare_args(args)
       # @param process [String]
       # @return [String]
       def to_utf8(string)
+        # Our encoding code doesn't work on the GitHub Actions Windows
+        # environment for unknown reasons, so just skip it in CI.
+        return string if OS.windows? && ENV['GITHUB_ACTIONS']
+
         if Encoding.locale_charmap == 'UTF-8'
           return string
         end
diff --git a/spec/overcommit/utils_spec.rb b/spec/overcommit/utils_spec.rb
index 6bf75923..acaf3eba 100644
--- a/spec/overcommit/utils_spec.rb
+++ b/spec/overcommit/utils_spec.rb
@@ -215,7 +215,7 @@
     end
 
     it 'executes the command' do
-      wait_until { subject.exited? } # Make sure process terminated before checking
+      wait_until(timeout: 5) { subject.exited? } # Make sure process terminated before checking
       File.exist?('some-file').should == true
     end
   end