diff --git a/tools/docker/build.sh b/tools/docker/build.sh
index 79617ca84..9996e6440 100755
--- a/tools/docker/build.sh
+++ b/tools/docker/build.sh
@@ -51,6 +51,10 @@ Build() {
 }
 
 TAG_BASE="$1"
+if [ -z "$TAG_BASE" ]; then
+    echo "We cannot tag Docker images with an empty string!" >&2
+    exit 1
+fi
 
 # Step 1: Certbot core Docker
 Build "$DOCKER_HUB_ORG/certbot" "$TAG_BASE" "$REPO_ROOT" "$WORK_DIR/core"
diff --git a/tools/docker/deploy.sh b/tools/docker/deploy.sh
index 89802f264..6b85ac0b6 100755
--- a/tools/docker/deploy.sh
+++ b/tools/docker/deploy.sh
@@ -24,6 +24,10 @@ Deploy() {
 }
 
 TAG_BASE="$1"  # Eg. v0.35.0 or nightly
+if [ -z "$TAG_BASE" ]; then
+    echo "We cannot tag Docker images with an empty string!" >&2
+    exit 1
+fi
 source "$WORK_DIR/lib/common"
 
 # Step 1: Certbot core Docker