diff --git a/appendix_python.ipynb b/appendix_python.ipynb
index a3d823dbb..7d3d1b173 100644
--- a/appendix_python.ipynb
+++ b/appendix_python.ipynb
@@ -1364,7 +1364,7 @@
       "sum = 0\n",
       "for i in xrange(10000):\n",
       "    # % is the modulo operator\n",
-      "    if x % 3 == 0 or x % 5 == 0:\n",
+      "    if i % 3 == 0 or i % 5 == 0:\n",
       "        sum += i\n"
      ],
      "language": "python",
@@ -3164,4 +3164,4 @@
    "metadata": {}
   }
  ]
-}
\ No newline at end of file
+}