diff --git a/src/ch/meson.build b/src/ch/meson.build
index 6311b84f3e..1d612a7369 100644
--- a/src/ch/meson.build
+++ b/src/ch/meson.build
@@ -60,7 +60,9 @@ if conf.has('WITH_CH')
   virt_daemon_units += {
     'service': 'virtchd',
     'name': 'Cloud Hypervisor',
-    'service_extra_in': files('virtchd.service.extra.in'),
+    'service_extra_in': [
+      files('virtchd.service.extra.in'),
+    ],
   }
 
   virt_install_dirs += [
diff --git a/src/libxl/meson.build b/src/libxl/meson.build
index 8e6f455139..e75a8f2fdb 100644
--- a/src/libxl/meson.build
+++ b/src/libxl/meson.build
@@ -67,8 +67,12 @@ if conf.has('WITH_LIBXL')
   virt_daemon_units += {
     'service': 'virtxend',
     'name': 'Xen',
-    'service_extra_in': files('virtxend.service.extra.in'),
-    'socket_extra_in': files('virtxend.socket.extra.in'),
+    'service_extra_in': [
+      files('virtxend.service.extra.in'),
+    ],
+    'socket_extra_in': [
+      files('virtxend.socket.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/lxc/meson.build b/src/lxc/meson.build
index 5eb23fbbbf..198e282e63 100644
--- a/src/lxc/meson.build
+++ b/src/lxc/meson.build
@@ -165,7 +165,9 @@ if conf.has('WITH_LXC')
   virt_daemon_units += {
     'service': 'virtlxcd',
     'name': 'LXC',
-    'service_extra_in': files('virtlxcd.service.extra.in'),
+    'service_extra_in': [
+      files('virtlxcd.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/meson.build b/src/meson.build
index 144f24e526..f3814d75ce 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -199,8 +199,8 @@ guest_unit_files = []
 #   * sockets - array of additional sockets (optional, default [ 'main', 'ro', 'admin' ])
 #   * service_in - service source file (optional, default virtd.service.in)
 #   * socket_$name_in - additional socket source files (optional, default virtd.socket.in or virtd-$name.socket.in)
-#   * service_extra_in - unit to merge with service_in (optional, default None)
-#   * socket_extra_in - unit to merge with socket_$name_in (optional, default None)
+#   * service_extra_in - units to merge with service_in (optional, default [])
+#   * socket_extra_in - units to merge with socket_$name_in (optional, default [])
 virt_daemon_units = []
 
 # openrc_init_files
@@ -824,9 +824,9 @@ if conf.has('WITH_LIBVIRTD')
 
       if 'service_extra_in' in unit
         service_in = configure_file(
-          input: [ service_in, unit['service_extra_in'] ],
+          input: [ service_in ] + unit['service_extra_in'],
           output: '@0@.in'.format(service_out),
-          command: [ merge_systemd_units_prog, '@INPUT0@', '@INPUT1@' ],
+          command: [ merge_systemd_units_prog, '@INPUT@' ],
           capture: true,
         )
       endif
@@ -852,9 +852,9 @@ if conf.has('WITH_LIBVIRTD')
 
         if 'socket_extra_in' in unit
           socket_in = configure_file(
-            input: [ socket_in, unit['socket_extra_in'] ],
+            input: [ socket_in ] + unit['socket_extra_in'],
             output: '@0@.in'.format(socket_out),
-            command: [ merge_systemd_units_prog, '@INPUT0@', '@INPUT1@' ],
+            command: [ merge_systemd_units_prog, '@INPUT@' ],
             capture: true,
           )
         endif
diff --git a/src/network/meson.build b/src/network/meson.build
index d0383cca1c..3cf2ef3d3d 100644
--- a/src/network/meson.build
+++ b/src/network/meson.build
@@ -63,7 +63,9 @@ if conf.has('WITH_NETWORK')
   virt_daemon_units += {
     'service': 'virtnetworkd',
     'name': 'network',
-    'service_extra_in': files('virtnetworkd.service.extra.in'),
+    'service_extra_in': [
+      files('virtnetworkd.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/qemu/meson.build b/src/qemu/meson.build
index 64c62e584f..fff61ddf27 100644
--- a/src/qemu/meson.build
+++ b/src/qemu/meson.build
@@ -184,7 +184,9 @@ if conf.has('WITH_QEMU')
   virt_daemon_units += {
     'service': 'virtqemud',
     'name': 'QEMU',
-    'service_extra_in': files('virtqemud.service.extra.in'),
+    'service_extra_in': [
+      files('virtqemud.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/storage/meson.build b/src/storage/meson.build
index 023353c1d6..daad8abf25 100644
--- a/src/storage/meson.build
+++ b/src/storage/meson.build
@@ -112,7 +112,9 @@ if conf.has('WITH_STORAGE')
   virt_daemon_units += {
     'service': 'virtstoraged',
     'name': 'storage',
-    'service_extra_in': files('virtstoraged.service.extra.in'),
+    'service_extra_in': [
+      files('virtstoraged.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/vbox/meson.build b/src/vbox/meson.build
index a72c1833f1..e05f532e35 100644
--- a/src/vbox/meson.build
+++ b/src/vbox/meson.build
@@ -58,7 +58,9 @@ if conf.has('WITH_VBOX')
   virt_daemon_units += {
     'service': 'virtvboxd',
     'name': 'VirtualBox',
-    'service_extra_in': files('virtvboxd.service.extra.in'),
+    'service_extra_in': [
+      files('virtvboxd.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {
diff --git a/src/vz/meson.build b/src/vz/meson.build
index ce2cbae454..bc5b5fb623 100644
--- a/src/vz/meson.build
+++ b/src/vz/meson.build
@@ -49,7 +49,9 @@ if conf.has('WITH_VZ')
   virt_daemon_units += {
     'service': 'virtvzd',
     'name': 'vz',
-    'service_extra_in': files('virtvzd.service.extra.in'),
+    'service_extra_in': [
+      files('virtvzd.service.extra.in'),
+    ],
   }
 
   openrc_init_files += {