diff --git a/nbs/core.ipynb b/nbs/core.ipynb
index 2bc187ac4..74b64ac00 100644
--- a/nbs/core.ipynb
+++ b/nbs/core.ipynb
@@ -40,6 +40,7 @@
    "outputs": [],
    "source": [
     "#| hide\n",
+    "import os\n",
     "import shutil\n",
     "import sys\n",
     "\n",