diff --git a/coordinator/backplane.lua b/coordinator/backplane.lua
index 310d042..f53a764 100644
--- a/coordinator/backplane.lua
+++ b/coordinator/backplane.lua
@@ -295,13 +295,13 @@ function backplane.attach(type, device, iface)
             end
         elseif wl_nic and m_is_wl then
             -- the wireless NIC already has a modem
+            device.closeAll()
+
             log_sys("standby wireless modem connected")
             log.info("BKPLN: standby wireless modem connected")
-        elseif wd_nic and wd_nic.is_modem(device) then
-            -- wired, but not active
-            log_sys("standby wired modem disconnected")
-            log.info("BKPLN: standby wired modem disconnected")
         else
+            device.closeAll()
+
             log_sys("unassigned modem connected")
             log.warning("BKPLN: unassigned modem connected")
         end
diff --git a/reactor-plc/backplane.lua b/reactor-plc/backplane.lua
index 07fd967..44ae3ff 100644
--- a/reactor-plc/backplane.lua
+++ b/reactor-plc/backplane.lua
@@ -209,9 +209,13 @@ function backplane.attach(iface, type, device, print_no_fp)
                 end
             elseif wl_nic and m_is_wl then
                 -- the wireless NIC already has a modem
+                device.closeAll()
+
                 print_no_fp("standby wireless modem connected")
                 log.info("BKPLN: standby wireless modem connected")
             else
+                device.closeAll()
+
                 print_no_fp("unassigned modem connected")
                 log.warning("BKPLN: unassigned modem connected")
             end
diff --git a/rtu/backplane.lua b/rtu/backplane.lua
index 0027579..00da9bb 100644
--- a/rtu/backplane.lua
+++ b/rtu/backplane.lua
@@ -157,9 +157,13 @@ function backplane.attach(type, device, iface, print_no_fp)
             end
         elseif wl_nic and m_is_wl then
             -- the wireless NIC already has a modem
+            device.closeAll()
+
             print_no_fp("standby wireless modem connected")
             log.info("BKPLN: standby wireless modem connected")
         else
+            device.closeAll()
+
             print_no_fp("unassigned modem connected")
             log.warning("BKPLN: unassigned modem connected")
         end
diff --git a/supervisor/backplane.lua b/supervisor/backplane.lua
index c88508b..535571f 100644
--- a/supervisor/backplane.lua
+++ b/supervisor/backplane.lua
@@ -111,9 +111,13 @@ function backplane.attach(iface, type, device, print_no_fp)
             databus.tx_hw_wl_modem(true)
         elseif _bp.wl_nic and m_is_wl then
             -- the wireless NIC already has a modem
+            device.closeAll()
+
             print_no_fp("standby wireless modem connected")
             log.info("BKPLN: standby wireless modem connected")
         else
+            device.closeAll()
+
             print_no_fp("unassigned modem connected")
             log.warning("BKPLN: unassigned modem connected")
         end