diff --git a/deploy.firebase.sh b/deploy.firebase.sh
index bf1754a..194d4e2 100755
--- a/deploy.firebase.sh
+++ b/deploy.firebase.sh
@@ -4,12 +4,13 @@ set -o pipefail
 set -e
 set -u
 
-if ! which firebase; then
+if tty && ! which firebase; then
    f="$(mktemp)"
    wget https://firebase.tools -O - > "$f"
    export upgrade=true
-   $(if tty &> /dev/null; then echo sudo; fi) sh "$f"
+   sudo bash "$f"
 fi
+which firebase
 
 outdir=./deploy