diff --git a/lectures/prob_dist.md b/lectures/prob_dist.md
index 22defb18..14c210c4 100644
--- a/lectures/prob_dist.md
+++ b/lectures/prob_dist.md
@@ -882,7 +882,7 @@ x_costco = prices.pct_change()[1:] * 100
 
 ```{code-cell} ipython3
 fig, ax = plt.subplots()
-ax.violinplot([x_amazon, x_costco])
+ax.violinplot([x_amazon['AMZN'], x_costco['COST']])
 ax.set_ylabel('monthly return (percent change)')
 ax.set_xlabel('retailers')