diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 871d3f6..5ef3904 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,30 +2,34 @@ name: CI
 on:
   pull_request:
     branches:
-      - 'master'
+      - "master"
   push:
     branches:
-      - 'master'
+      - "master"
 jobs:
   build-test:
     name: Build and test on Erlang/OTP ${{ matrix.otp_version }} and ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        otp_version: [23, 24, '25.1.1']
-        os: [ubuntu-latest, windows-latest]
+        otp_version: ["23", "24", "25.1.1"]
+        os:
+          # TODO: change to ubuntu-latest after OTP 23 is deprecated, see
+          # https://github.com/erlef/setup-beam#compatibility-between-operating-system-and-erlangotp
+          - ubuntu-20.04
+          - windows-latest
     env:
-      LATEST_OTP_RELEASE: '25.1.1'
+      LATEST_OTP_RELEASE: "25.1.1"
     steps:
       - uses: actions/checkout@v3
       - uses: erlef/setup-beam@v1
         id: install-erlang
         with:
           otp-version: ${{matrix.otp_version}}
-          rebar3-version: '3.19'
+          rebar3-version: "3.19"
       - name: Restore Dialyzer PLT files from cache
         uses: actions/cache@v3
-        if: ${{ matrix.otp_version == env.LATEST_OTP_RELEASE && matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.otp_version == env.LATEST_OTP_RELEASE && startsWith(matrix.os, 'ubuntu') }}
         with:
           path: _build/*/rebar3_*_plt
           key: dialyzer-plt-cache-${{ steps.install-erlang.outputs.otp-version }}-${{ runner.os }}-${{ hashFiles('rebar.config*') }}-v0
@@ -38,5 +42,5 @@ jobs:
           ERL_FLAGS: "+pc unicode"
         run: rebar3 eunit --verbose
       - name: Dialyzer
-        if: ${{ matrix.otp_version == env.LATEST_OTP_RELEASE && matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.otp_version == env.LATEST_OTP_RELEASE && startsWith(matrix.os, 'ubuntu') }}
         run: rebar3 dialyzer