diff --git a/vignettes/ml100k.Rmd b/vignettes/ml100k.Rmd
index 3d2230e..cb928be 100644
--- a/vignettes/ml100k.Rmd
+++ b/vignettes/ml100k.Rmd
@@ -22,6 +22,7 @@ knitr::opts_chunk$set(
 # install.packages("devtools")
 # devtools::install_github("YangLabHKUST/mfair")
 library(mfair)
+library(Matrix)
 library(reshape2)
 library(ggplot2)
 library(scales)