diff --git a/1. Message Structure/Lesson.ipynb b/1. Message Structure/Lesson.ipynb
index 71b685a..efbea58 100644
--- a/1. Message Structure/Lesson.ipynb	
+++ b/1. Message Structure/Lesson.ipynb	
@@ -415,7 +415,9 @@
     "Now how should we deal with these magic bytes in the process of reading and interpreting real Bitcoin network messages? This one is pretty simple -- just check whether they're equal to the values in the wiki / reference implementation!\n",
     "\n",
     "![image](../images/magic-values.png)\n",
-    "##### Exercise 2: Check Network Magic"
+    "##### Exercise 2: Check Network Magic",
+    "\n",
+    "Try and fix the code below to get all the tests to pass:\n"
    ]
   },
   {
@@ -427,7 +429,7 @@
     "NETWORK_MAGIC = b'\\xf9\\xbe\\xb4\\xd9'\n",
     "\n",
     "def read_magic(stream):\n",
-    "    raise NotImplementedError()\n",
+    "    raise ImplementMeToMakeItWork() # What does this line need to be replaced with? \n", 
     "\n",
     "def is_mainnet_msg(stream):\n",
     "    magic = read_magic(stream)\n",
@@ -581,7 +583,7 @@
    "outputs": [],
    "source": [
     "def read_length(stream):\n",
-    "    raise NotImplementedError()"
+    "    raise NotImplementedError() # Fix me!"
    ]
   },
   {
@@ -726,8 +728,6 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Where Bitcoin uses SHA256, it usually uses it twice. [Here's a discussion](https://bitcoin.stackexchange.com/questions/6037/why-are-hashes-in-the-bitcoin-protocol-typically-computed-twice-double-computed) of why Satoshi might have made this decision  \n",
-    "\n",
     "##### Exercise 8: Write a `compute_checksum` function which returns the first four bytes of \"double-sha256\""
    ]
   },
@@ -782,7 +782,7 @@
     "\n",
     "print(\"Payload: \", payload)\n",
     "\n",
-    "print(\"checksum == compute_checksum(payload)?: \", \n",
+    "print(\"Is the received checksum the same as the computed checksum?: \", \n",
     "      checksum == compute_checksum(payload))"
    ]
   },