diff --git a/Lambda/build-mac-app.sh b/Lambda/build-mac-app.sh
index 3ab2f35..ccc2c38 100755
--- a/Lambda/build-mac-app.sh
+++ b/Lambda/build-mac-app.sh
@@ -11,6 +11,11 @@ fi
 OUTPUT_DIR=${CD}/product
 APP_ROOT=${OUTPUT_DIR}/LambdaMagica.app
 
+if [ -e ${APP_ROOT} ]; then
+  echo "Deleting existing ${APP_ROOT}"
+  rm -r ${APP_ROOT}
+fi
+
 CONTENTS=${APP_ROOT}/Contents
 EXECUTABLE=${CONTENTS}/MacOS/run.sh