diff --git a/bin/install-site.sh b/bin/install-site.sh
index 82885c78..3be51f68 100755
--- a/bin/install-site.sh
+++ b/bin/install-site.sh
@@ -141,17 +141,14 @@ update_apt_sources() {
         esac
     elif [ x"$DISTRIBUTION" = x"debian" ] ; then
         case "$DISTVERSION" in
-            buster)
-                BACKPORTS=false
-                SECURITY="$DISTVERSION/updates"
-                ;;
             bullseye)
                 BACKPORTS=false
-                SECURITY="$DISTVERSION-security"
                 ;;
             bookworm)
                 BACKPORTS=false
-                SECURITY="$DISTVERSION-security"
+                ;;
+            trixie)
+                BACKPORTS=false
                 ;;
             *)
                 notice_msg "Unsupported distribution and version combination $DISTRIBUTION $DISTVERSION"
@@ -170,7 +167,7 @@ Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
 # Security Updates:
 Types: deb deb-src
 URIs: http://deb.debian.org/debian-security
-Suites: $SECURITY
+Suites: $DISTVERSION-security
 Components: main contrib non-free
 Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
 
@@ -200,7 +197,7 @@ update_mysociety_apt_sources() {
     # We build packages targetted at Debian releases.
     # Try and select the most appropritate ones for Ubuntu.
     case "$DISTVERSION" in
-        focal|jammy|buster|bullseye|bookworm)
+        focal|jammy|bullseye|bookworm|trixie)
             cat > /etc/apt/sources.list.d/mysociety.sources <<EOF
 Types: deb
 URIs: http://debian.mysociety.org
diff --git a/shlib/installfns b/shlib/installfns
index 2cac6181..96a2d9e3 100755
--- a/shlib/installfns
+++ b/shlib/installfns
@@ -141,17 +141,14 @@ update_apt_sources() {
         esac
     elif [ x"$DISTRIBUTION" = x"debian" ] ; then
         case "$DISTVERSION" in
-            buster)
-                BACKPORTS=false
-                SECURITY="$DISTVERSION/updates"
-                ;;
             bullseye)
                 BACKPORTS=false
-                SECURITY="$DISTVERSION-security"
                 ;;
             bookworm)
                 BACKPORTS=false
-                SECURITY="$DISTVERSION-security"
+                ;;
+            trixie)
+                BACKPORTS=false
                 ;;
             *)
                 notice_msg "Unsupported distribution and version combination $DISTRIBUTION $DISTVERSION"
@@ -170,7 +167,7 @@ Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
 # Security Updates:
 Types: deb deb-src
 URIs: http://deb.debian.org/debian-security
-Suites: $SECURITY
+Suites: $DISTVERSION-security
 Components: main contrib non-free
 Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
 
@@ -200,7 +197,7 @@ update_mysociety_apt_sources() {
     # We build packages targetted at Debian releases.
     # Try and select the most appropritate ones for Ubuntu.
     case "$DISTVERSION" in
-        focal|jammy|buster|bullseye|bookworm)
+        focal|jammy|bullseye|bookworm|trixie)
             cat > /etc/apt/sources.list.d/mysociety.sources <<EOF
 Types: deb
 URIs: http://debian.mysociety.org