diff --git a/notebooks/intro_to_programming/raw/ex1.ipynb b/notebooks/intro_to_programming/raw/ex1.ipynb
index c341c7355..3955ba776 100644
--- a/notebooks/intro_to_programming/raw/ex1.ipynb
+++ b/notebooks/intro_to_programming/raw/ex1.ipynb
@@ -333,7 +333,7 @@
     "print(survived)\n",
     "\n",
     "# Number of passengers under 18\n",
-    "minors = (titanic_data.Age < 18).sum()\n",
+    "minors = (titanic_data.Age.dropna() < 18).sum()\n",
     "print(minors)"
    ]
   },