diff --git a/bitcoin/dumbcoin/dumbcoin.ipynb b/bitcoin/dumbcoin/dumbcoin.ipynb
index 66928e7..7f305bf 100644
--- a/bitcoin/dumbcoin/dumbcoin.ipynb
+++ b/bitcoin/dumbcoin/dumbcoin.ipynb
@@ -170,7 +170,7 @@
     "        nonce: The found nonce\n",
     "        niters: The number of iterations required to find the nonce\n",
     "    \"\"\"\n",
-    "    assert difficulty >= 1, \"Difficulty of 0 is not possible\"\n",
+    "    assert difficulty >= 1 \"Difficulty of 0 is not possible\"\n",
     "    i = 0\n",
     "    prefix = '1' * difficulty\n",
     "    while True:\n",