diff --git a/tutorial.ipynb b/tutorial.ipynb
index 8374153..26a3e1f 100644
--- a/tutorial.ipynb
+++ b/tutorial.ipynb
@@ -42,6 +42,8 @@
     "export WORK_DIR=$HOME/WORK\n",
     "if ! [ -d $WORK_DIR ]; then\n",
     "    mkdir -p $WORK_DIR\n",
+    "    fi\n",
+    "if ! [ -e $WORK_DIR/_mapper ]; then\n",
     "    echo \"lsst.obs.hsc.HscMapper\" > $WORK_DIR/_mapper\n",
     "    ingestImages.py $WORK_DIR $CI_HSC_DIR/raw/*.fits --mode=link\n",
     "    cd $WORK_DIR\n",