diff --git a/lectures/mix_model.md b/lectures/mix_model.md
index feeb623..76c7ad2 100644
--- a/lectures/mix_model.md
+++ b/lectures/mix_model.md
@@ -116,6 +116,7 @@ $$
 :hide-output: false
 
 import matplotlib.pyplot as plt
+import matplotlib as mpl
 FONTPATH = "fonts/SourceHanSerifSC-SemiBold.otf"
 mpl.font_manager.fontManager.addfont(FONTPATH)
 plt.rcParams['font.family'] = ['Source Han Serif SC']