diff --git a/debian/systemd/koha-indexer@.service b/debian/systemd/koha-indexer@.service
index a7655e3655..2818161f5b 100644
--- a/debian/systemd/koha-indexer@.service
+++ b/debian/systemd/koha-indexer@.service
@@ -16,7 +16,10 @@ Environment=KOHA_HOME=/usr/share/koha
 Environment=PERL5LIB=/usr/share/koha/lib
 ExecStartPre=+/usr/sbin/koha-generate-env indexer %i
 EnvironmentFile=-/run/koha/%i/indexer.env
-ExecStart=/usr/share/koha/bin/migration_tools/rebuild_zebra.pl -daemon -sleep ${INDEXER_TIMEOUT}
+# INDEXER_DAEMON honours ALTERNATE_INDEXER_DAEMON and INDEXER_PARAMS from
+# /etc/default/koha-common, resolved by koha-generate-env like koha-indexer
+# does. $INDEXER_PARAMS is unbraced on purpose so it is split into arguments.
+ExecStart=/usr/bin/env ${INDEXER_DAEMON} $INDEXER_PARAMS
 ProtectSystem=full
 ProtectHome=yes
 PrivateTmp=yes
diff --git a/debian/systemd/koha-z3950@.service b/debian/systemd/koha-z3950@.service
index 8ad484b1c3..791c2044fa 100644
--- a/debian/systemd/koha-z3950@.service
+++ b/debian/systemd/koha-z3950@.service
@@ -17,8 +17,11 @@ Environment=PERL5LIB=/usr/share/koha/lib
 PIDFile=/run/koha/%i/z3950-responder.pid
 ExecStartPre=+/usr/sbin/koha-generate-env z3950 %i
 EnvironmentFile=-/run/koha/%i/z3950.env
-ExecStart=/usr/share/koha/bin/z3950_responder.pl \
-    ${Z3950_ADDITIONAL_OPTS} \
+# $Z3950_ADDITIONAL_OPTS is deliberately unbraced: systemd splits "$VAR" into
+# separate arguments (and into none when empty) whereas "${VAR}" is always
+# exactly one argument.
+ExecStart=/usr/bin/perl /usr/share/koha/bin/z3950_responder.pl \
+    $Z3950_ADDITIONAL_OPTS \
     --config-dir ${Z3950_CONFIGDIR} \
     -u %i-koha \
     -p /run/koha/%i/z3950-responder.pid \