diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 28be095cb3..268eff68b8 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -13,11 +13,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        os: [alpine-3.17, ubuntu-20.04, ubuntu-22.04]
+        os: [alpine-3.17, alpine-3.21, ubuntu-20.04, ubuntu-22.04]
         platform: [linux/amd64]
         include:
           - os: alpine-3.17
             platform: linux/arm64
+          - os: alpine-3.21
+            platform: linux/arm64
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
diff --git a/Earthfile b/Earthfile
index e19cb9f550..7064396cbb 100644
--- a/Earthfile
+++ b/Earthfile
@@ -10,6 +10,17 @@ alpine-3.17:
       rm -rf /var/cache/apk/*
   RUN apk add openjdk8-jre
 
+alpine-3.21:
+  FROM --platform=$BUILDPLATFORM alpine:3.21
+  RUN apk add --no-progress --update git build-base zip
+  RUN apk --no-cache --update add libgcc libstdc++ \
+      git make g++ \
+      build-base gtest gtest-dev boost boost-dev protobuf protobuf-dev cmake icu icu-dev openssl \
+      && \
+      rm -rf /var/cache/apk/*
+  RUN apk add openjdk8-jre
+  ENV LIB_DEPS=absl::absl_check
+
 ubuntu-20.04:
   FROM --platform=$BUILDPLATFORM ubuntu:20.04
   RUN apt-get update && apt-get -y upgrade
@@ -47,10 +58,12 @@ libphonenumber:
 
   WORKDIR /libphonenumber/cpp/build
   RUN mkdir assets
-  RUN cmake -DCMAKE_INSTALL_PREFIX:PATH=./assets ..
+  RUN sed -i 's/absl::synchronization/absl::synchronization ${LIB_DEPS}/' ../CMakeLists.txt
+  RUN cmake -DLIB_DEPS=${LIB_DEPS} -DCMAKE_INSTALL_PREFIX:PATH=./assets ..
   RUN make install
 
   WORKDIR assets
+  RUN rm -rf lib/cmake
   RUN zip -r ../libphonenumber_${TARGETARCH}-${buildos}.zip *
 
   SAVE ARTIFACT /libphonenumber/cpp/build/libphonenumber_${TARGETARCH}-${buildos}.zip AS LOCAL cpp/build/libphonenumber_${TARGETARCH}-${buildos}.zip