diff --git a/src/main b/src/main
index f963016..7561599 100755
--- a/src/main
+++ b/src/main
@@ -64,17 +64,22 @@ REQUIRED_PACKAGES=(
 
 echo "# configure apt sources to the mithril's"
 echo "========================================"
-echo "deb http://debian.mithril.re/debian bullseye main contrib non-free" | sudo tee /etc/apt/sources.list
-echo "deb http://debian.mithril.re/debian bullseye-updates main contrib non-free" | sudo tee -a /etc/apt/sources.list
-echo "deb http://debian.mithril.re/debian-security/ bullseye-security main contrib non-free" | sudo tee -a /etc/apt/sources.list
 
-echo "# updating repositories"
-echo "==================="
-if [[ $(date --date='-12 hours' +%s) -gt $(date -d "$(stat -c %y /var/lib/apt/lists/partial)" +%s) ]]; then
+if ! grep -q debian.mithril.re /etc/apt/sources.list; then
+    echo "deb http://debian.mithril.re/debian bullseye main contrib non-free" | sudo tee /etc/apt/sources.list
+    echo "deb http://debian.mithril.re/debian bullseye-updates main contrib non-free" | sudo tee -a /etc/apt/sources.list
+    echo "deb http://debian.mithril.re/debian-security/ bullseye-security main contrib non-free" | sudo tee -a /etc/apt/sources.list
     sudo apt update
     sudo apt autoremove -y
 else
-    echo "repositories recently updated!"
+    echo "# updating repositories"
+    echo "==================="
+    if [[ $(date --date='-12 hours' +%s) -gt $(date -d "$(stat -c %y /var/lib/apt/lists/partial)" +%s) ]]; then
+        sudo apt update
+        sudo apt autoremove -y
+    else
+        echo "repositories recently updated!"
+    fi
 fi
 
 echo "# required packages"