diff --git a/render-wasm/watch b/render-wasm/watch
index 59139ec2cb..5ead50c188 100755
--- a/render-wasm/watch
+++ b/render-wasm/watch
@@ -13,6 +13,8 @@ copy_shared_artifact;
 pushd $_SCRIPT_DIR;
 
 cargo watch \
+      --why \
+      -i "_tmp*"
       -x "build $CARGO_PARAMS" \
       -s "./build" \
       -s "echo 'DONE\n'";