diff --git a/actions/gapic/action.yml b/actions/gapic/action.yml
index 2443726..dbebd87 100644
--- a/actions/gapic/action.yml
+++ b/actions/gapic/action.yml
@@ -36,6 +36,10 @@ inputs:
   dry_run:
     description: "Do not push changes"
     required: false
+  upstream:
+    description: Default branch of repository
+    default: master
+    required: false
 runs:
   using: "docker"
   image: "Dockerfile"
diff --git a/actions/gapic/entrypoint.sh b/actions/gapic/entrypoint.sh
index d8eb752..40204fe 100755
--- a/actions/gapic/entrypoint.sh
+++ b/actions/gapic/entrypoint.sh
@@ -7,7 +7,7 @@ TARGET_DIR=$(echo $INPUT_TARGET | sed 's/:/\//g' | sed 's/^\/*//g')
 TARGET_OUTPUT="${TARGET_DIR}.tar.gz"
 SLUG=$(echo $INPUT_TARGET | sed 's/^\/*//g' | sed 's/[\/.:]/_/g')
 BRANCH="__gapic_action__/${SLUG}"
-
+UPSTREAM="$INPUT_UPSTREAM";
 TEMP_GIT_GOOGLEAPIS=$(mktemp -d)
 TEMP_GIT_LOCAL=$(mktemp -d)
 GOOGLE_APPLICATION_CREDENTIALS=$(mktemp)
@@ -16,7 +16,7 @@ GOOGLE_APPLICATION_CREDENTIALS=$(mktemp)
 
 pushd $TEMP_GIT_GOOGLEAPIS
 
-git clone --single-branch --branch master https://github.com/googleapis/googleapis.git .
+git clone --single-branch --branch "$UPSTREAM" https://github.com/googleapis/googleapis.git .
 
 set +x # WARNING: do not remove
 if [[ -n "${INPUT_CACHE_SERVICE_ACCOUNT}" ]]; then
@@ -41,16 +41,16 @@ git config --global user.name $INPUT_GIT_NAME
 git checkout -B $BRANCH
 
 # reset since this may run in cron
-git reset --hard origin/master
+git reset --hard "origin/$UPSTREAM"
 
 # extract the tar to the correct location
 tar xf "${TEMP_GIT_GOOGLEAPIS}/bazel-bin/${TARGET_OUTPUT}" --strip-components $INPUT_TAR_STRIP_COMPONENTS $INPUT_TAR_PATH
 
 #### PUBLISH COMMITS ####
 
-[[ -n $(git diff "origin/master") ]] && differs_from_master=1 || differs_from_master=0
+[[ -n $(git diff "origin/$UPSTREAM") ]] && differs_from_upstream=1 || differs_from_upstream=0
 
-if [ $differs_from_master ]; then
+if [ $differs_from_upstream ]; then
     set -x
 
     git add -A
@@ -76,7 +76,7 @@ if [ $differs_from_master ]; then
             -H "Authorization: Bearer ${INPUT_GITHUB_TOKEN}" \
             -H "Content-Type:application/json" \
             -X POST https://api.github.com/repos/${GITHUB_REPOSITORY}/pulls \
-            -d "{\"title\":\"GAPIC Client Update: ${INPUT_TARGET}\", \"body\": \"\", \"head\": \"$BRANCH\", \"base\": \"master\"}"
+            -d "{\"title\":\"GAPIC Client Update: ${INPUT_TARGET}\", \"body\": \"\", \"head\": \"$BRANCH\", \"base\": \"$UPSTREAM\"}"
     fi
 
 fi