diff --git a/README.md b/README.md
index 04af819..1dcd6cb 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,8 @@ ttyd is a simple command-line tool for sharing terminal over the web.
 - Install the snap: `sudo snap install ttyd --classic`
 - Build from source (debian/ubuntu):
     ```bash
-    sudo apt-get install build-essential cmake git libjson-c-dev libwebsockets-dev
+    sudo apt-get update
+    sudo apt-get install -y build-essential cmake git libjson-c-dev libwebsockets-dev
     git clone https://github.com/tsl0922/ttyd.git
     cd ttyd && mkdir build && cd build
     cmake ..