diff --git a/debian/control b/debian/control
index a9acc27f0e..b7f8286b71 100644
--- a/debian/control
+++ b/debian/control
@@ -498,6 +498,8 @@ Architecture: all
 Depends: ${misc:Depends}, daemon, koha-core
 Provides: koha-init
 Conflicts: koha-systemd
+Replaces: koha-common (<< 25.11)
+Breaks: koha-common (<< 25.11)
 Description: SysV init scripts for Koha ILS
  Koha is an Integrated Library Management system for real-world libraries
  (the kinds with books).
diff --git a/debian/control.in b/debian/control.in
index 8b9a02450a..9703bc3f40 100644
--- a/debian/control.in
+++ b/debian/control.in
@@ -162,6 +162,8 @@ Architecture: all
 Depends: ${misc:Depends}, daemon, koha-core
 Provides: koha-init
 Conflicts: koha-systemd
+Replaces: koha-common (<< 25.11)
+Breaks: koha-common (<< 25.11)
 Description: SysV init scripts for Koha ILS
  Koha is an Integrated Library Management system for real-world libraries
  (the kinds with books).
diff --git a/debian/koha-systemd.postinst b/debian/koha-systemd.postinst
index ab66ad23b0..3e5593e0a5 100644
--- a/debian/koha-systemd.postinst
+++ b/debian/koha-systemd.postinst
@@ -6,6 +6,23 @@ case "$1" in
         # Reload systemd daemon
         systemctl daemon-reload || true
 
+        # Stop and disable the legacy SysV koha-common.service if present.
+        # This service is auto-generated by systemd-sysv-generator from
+        # /etc/init.d/koha-common and would run in parallel with the native
+        # systemd units, causing double-starts.
+        if systemctl is-active --quiet koha-common.service 2>/dev/null; then
+            systemctl stop koha-common.service || true
+        fi
+        if systemctl is-enabled --quiet koha-common.service 2>/dev/null; then
+            systemctl disable koha-common.service || true
+        fi
+        # Remove the orphaned SysV init script if it was left behind by
+        # the old koha-common package (pre-split) and koha-sysv is not installed.
+        if [ -f /etc/init.d/koha-common ] && ! dpkg -s koha-sysv >/dev/null 2>&1; then
+            rm -f /etc/init.d/koha-common
+            systemctl daemon-reload || true
+        fi
+
         # On first install (no previous version), enable units for all existing instances
         # This handles migration from SysV init to systemd
         if [ -z "$2" ]; then