diff --git a/.cirrus.yml b/.cirrus.yml
index 3f48455c5d85..50f567fd2fe7 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -182,6 +182,9 @@ task:
     ### Android tasks ###
     - name: android-platform_tests
       env:
+        matrix:
+          PACKAGE_SHARDING: "--shardIndex 0 --shardCount 2"
+          PACKAGE_SHARDING: "--shardIndex 1 --shardCount 2"
         matrix:
           CHANNEL: "master"
           CHANNEL: "stable"
diff --git a/script/tool_runner.sh b/script/tool_runner.sh
index 7029a53c80a2..9b87f98e30df 100755
--- a/script/tool_runner.sh
+++ b/script/tool_runner.sh
@@ -8,6 +8,9 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
 REPO_DIR="$(dirname "$SCRIPT_DIR")"
 
 # The tool expects to be run from the repo root.
+# PACKAGE_SHARDING is (optionally) set from Cirrus. See .cirrus.yml
 cd "$REPO_DIR"
-dart pub global run flutter_plugin_tools "$@" --packages-for-branch \
-  --log-timing $BUILD_SHARDING
+dart pub global run flutter_plugin_tools "$@" \
+  --packages-for-branch \
+  --log-timing \
+  $PACKAGE_SHARDING