diff --git a/code/chap02.ipynb b/code/chap02.ipynb
index 04fad62e..58fcc17e 100644
--- a/code/chap02.ipynb
+++ b/code/chap02.ipynb
@@ -447,7 +447,7 @@
    "source": [
     "## Amplitude and phase\n",
     "\n",
-    "Make a triangle wave."
+    "Make a sawtooth wave."
    ]
   },
   {
@@ -691,6 +691,7 @@
    "outputs": [],
    "source": [
     "i = complex(0, 1)\n",
+    "spectrum = wave.make_spectrum()\n",
     "spectrum.hs = magnitude * np.exp(i * angle)"
    ]
   },