diff --git a/src/main/java/li/cil/oc2/common/blockentity/NetworkSwitchTileEntity.java b/src/main/java/li/cil/oc2/common/blockentity/NetworkSwitchTileEntity.java
index 2293b108..95ab3f80 100644
--- a/src/main/java/li/cil/oc2/common/blockentity/NetworkSwitchTileEntity.java
+++ b/src/main/java/li/cil/oc2/common/blockentity/NetworkSwitchTileEntity.java
@@ -50,7 +50,10 @@ public void writeEthernetFrame(final NetworkInterface source, final byte[] frame
                 // if packet is to same port, drop
                 return;
             }
-            adjacentInterfaces[host.iface].writeEthernetFrame(this, frame, timeToLive - TTL_COST);
+            NetworkInterface iface = adjacentInterfaces[host.iface];
+            if (iface != null) {
+                iface.writeEthernetFrame(this, frame, timeToLive - TTL_COST);
+            }
             host.timestamp = tickTime;
         } else {
             super.writeEthernetFrame(source, frame, timeToLive);