diff --git a/numbat-wasm/deploy.sh b/numbat-wasm/deploy.sh
index a7369bfa..baf7e76f 100644
--- a/numbat-wasm/deploy.sh
+++ b/numbat-wasm/deploy.sh
@@ -2,6 +2,13 @@
 
 set -euo pipefail
 
+current_branch=$(git rev-parse --abbrev-ref HEAD)
+
+if [[ "$current_branch" != "master" ]]; then
+    echo "You are currently on the '$current_branch' branch, not 'master'."
+    exit 1
+fi
+
 wasm-pack build --features=wee_alloc
 
 (