diff --git a/src/bookworm b/src/bookworm
index 6e09e4e..b15142e 100755
--- a/src/bookworm
+++ b/src/bookworm
@@ -64,7 +64,7 @@ REQUIRED_PACKAGES=(
 
 echo "# configure apt sources to the mithril's"
 echo "========================================"
-if grep debian-src /etc/apt/sources.list; then
+if grep cdrom /etc/apt/sources.list; then
     echo "deb http://debian.mithril.re/debian bookworm main contrib non-free-firmware" | sudo tee /etc/apt/sources.list
     echo "deb http://debian.mithril.re/debian bookworm-updates main contrib non-free-firmware" | sudo tee -a /etc/apt/sources.list
     echo "deb http://debian.mithril.re/debian-security bookworm-security main contrib non-free-firmware" | sudo tee -a /etc/apt/sources.list