diff --git a/src/main/scala/li/cil/oc/server/driver/Registry.scala b/src/main/scala/li/cil/oc/server/driver/Registry.scala
index 9f2b388e2..0a7a69fbe 100644
--- a/src/main/scala/li/cil/oc/server/driver/Registry.scala
+++ b/src/main/scala/li/cil/oc/server/driver/Registry.scala
@@ -113,7 +113,7 @@ private[oc] object Registry extends api.detail.DriverAPI {
       memo.get(valueRef)
     }
     else valueRef match {
-      case null | None => null
+      case null | Unit | None => null
 
       case arg: java.lang.Boolean => arg
       case arg: java.lang.Byte => arg