diff --git a/content/07a_opcodes/02_math.ipynb b/content/07a_opcodes/02_math.ipynb
index 4c3513a..33378d6 100644
--- a/content/07a_opcodes/02_math.ipynb
+++ b/content/07a_opcodes/02_math.ipynb
@@ -195,7 +195,7 @@
     "def mulmod(evm):\n",
     "    a, b = evm.stack.pop(), evm.stack.pop()\n",
     "    N = evm.stack.pop()\n",
-    "    evm.stack.push((a + b) * N)\n",
+    "    evm.stack.push((a * b) % N)\n",
     "    evm.pc += 1\n",
     "    evm.gas_dec(8)"
    ]