diff --git a/ci/r.yml b/ci/r.yml
index fb959bf..cad232b 100644
--- a/ci/r.yml
+++ b/ci/r.yml
@@ -1,23 +1,37 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+#
+# See https://github.com/r-lib/actions/tree/master/examples#readme for
+# additional example workflows available for the R community.
+
 name: R
 
-on: [push]
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
 
 jobs:
   build:
-
     runs-on: macOS-latest
     strategy:
-      max-parallel: 4
       matrix:
-        r-version: [3.5.3, 3.6.1]
+        r-version: [3.5, 3.6]
 
     steps:
-    - uses: actions/checkout@v1
-    - name: Set up R ${{ matrix.r-version }}
-      uses: rlib/actions/setup-r@v1
-      with:
-        r-version: ${{ matrix.r-version }}
-    - name: Install dependencies
-      run: Rscript -e "install.packages(c('remotes', 'rcmdcheck'))" -e "remotes::install_deps(dependencies = TRUE)"
-    - name: Check
-      run: Rscript -e "rcmdcheck::rcmdcheck(args = '--no-manual', error_on = 'error')"
+      - uses: actions/checkout@v2
+      - name: Set up R ${{ matrix.r-version }}
+        uses: r-lib/actions/setup-r@ffe45a39586f073cc2e9af79c4ba563b657dc6e3
+        with:
+          r-version: ${{ matrix.r-version }}
+      - name: Install dependencies
+        run: |
+          install.packages(c("remotes", "rcmdcheck"))
+          remotes::install_deps(dependencies = TRUE)
+        shell: Rscript {0}
+      - name: Check
+        run: rcmdcheck::rcmdcheck(args = "--no-manual", error_on = "error")
+        shell: Rscript {0}