diff --git a/15_autoencoders.ipynb b/15_autoencoders.ipynb
index b483acfe2..1301f3f55 100644
--- a/15_autoencoders.ipynb
+++ b/15_autoencoders.ipynb
@@ -43,6 +43,7 @@
     "import numpy as np\n",
     "import numpy.random as rnd\n",
     "import os\n",
+    "import sys\n",
     "\n",
     "# to make this notebook's output stable across runs\n",
     "rnd.seed(42)\n",