diff --git a/debian/changelog b/debian/changelog
index 727f324..a4e48a3 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -9,6 +9,11 @@ ubuntu-dev-tools (0.192) UNRELEASED; urgency=medium
   * Demote bzr/brz from Recommends to Suggests, as nowadays git is the way.
     Closes: #940531
 
+  [ Masahiro Yamada ]
+  * mk-sbuild:
+    + Handle the new location of the Debian bullseye security archive.
+      Closes: #1001832; LP: #1955116
+
  -- Mattia Rizzolo <mattia@debian.org>  Tue, 11 Oct 2022 13:57:46 +0200
 
 ubuntu-dev-tools (0.191) unstable; urgency=medium
diff --git a/mk-sbuild b/mk-sbuild
index e280fbb..52e15a1 100755
--- a/mk-sbuild
+++ b/mk-sbuild
@@ -397,29 +397,41 @@ fi
 # By default DEBOOTSTRAP_SCRIPT must match RELEASE
 DEBOOTSTRAP_SCRIPT="$RELEASE"
 
-if [ "$DISTRO" = "ubuntu" ]; then
-    ubuntu_dist_ge() {
-      local releases="$(ubuntu-distro-info --all)"
-      local left=999
-      local right=0
-      local seq=1
-      for i in $releases; do
+dist_ge() {
+    local releases="$($3-distro-info --all)"
+    local left=999
+    local right=0
+    local seq=1
+
+    for i in $releases; do
         if [ $1 = $i ]; then
-          local left=$seq
-          break
+            local left=$seq
+            break
         fi
         seq=$((seq+1))
-      done
-      seq=1
-      for i in $releases; do
+    done
+
+    seq=1
+    for i in $releases; do
         if [ $2 = $i ]; then
-          local right=$seq
-          break
+            local right=$seq
+            break
         fi
         seq=$((seq+1))
-      done
-      [ $left -ge $right ] && return 0 || return 1
-    }
+    done
+
+    [ $left -ge $right ] && return 0 || return 1
+}
+
+ubuntu_dist_ge () {
+    dist_ge $1 $2 ubuntu
+}
+
+debian_dist_ge () {
+    dist_ge $1 $2 debian
+}
+
+if [ "$DISTRO" = "ubuntu" ]; then
     # On Ubuntu, set DEBOOTSTRAP_SCRIPT to gutsy to allow building new RELEASES without new debootstrap
     DEBOOTSTRAP_SCRIPT=gutsy
 fi
@@ -663,7 +675,11 @@ debian)
     # Debian only performs security updates
     SKIP_UPDATES=1
     if [ -z "$SOURCES_SECURITY_SUITE" ]; then
-        SOURCES_SECURITY_SUITE="RELEASE/updates"
+        if debian_dist_ge "$RELEASE" "bullseye"; then
+            SOURCES_SECURITY_SUITE="RELEASE-security"
+        else
+            SOURCES_SECURITY_SUITE="RELEASE/updates"
+        fi
     fi
     if [ -z "$SOURCES_SECURITY_URL" ]; then
         SOURCES_SECURITY_URL="http://security.debian.org/"