diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 546e8b0..d071080 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,14 +8,31 @@ jobs:
   test:
     name: Test
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - macos-latest
+        - windows-latest
+        ruby_version:
+        - 2.7
+        - 2.6
+        - 2.5
+        - 2.4
+        - jruby
+        - truffleruby
 
     steps:
     - uses: actions/checkout@v1
-    - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+
+    - name: Setup Ruby
+      uses: eregon/use-ruby-action@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: ${{ matrix.ruby_version }}
+
     - name: Build and test with Rake
       run: |
         gem install bundler
diff --git a/lib/colors/convert.rb b/lib/colors/convert.rb
index 5dcf74e..ee741f0 100644
--- a/lib/colors/convert.rb
+++ b/lib/colors/convert.rb
@@ -53,7 +53,7 @@ def max_chroma(l, h)
 
     # degree -> ???
 
-    DEG2RAD = 0.01745329251994329577r  # 2 * pi / 360
+    DEG2RAD = 1745329251994329577/100000000000000000000r  # 2 * pi / 360
     def degree_to_radian(d)
       d * DEG2RAD
     end