diff --git a/src/main/scala/li/cil/oc/server/machine/Machine.scala b/src/main/scala/li/cil/oc/server/machine/Machine.scala
index b25c18bb4..f41ca7613 100644
--- a/src/main/scala/li/cil/oc/server/machine/Machine.scala
+++ b/src/main/scala/li/cil/oc/server/machine/Machine.scala
@@ -117,19 +117,17 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
       }
       case _ => 0
     }))
-    val oldArchitecture = architecture
-    architecture = null
+    var newArchitecture: Architecture = null
     components.find {
       case stack: ItemStack => Option(Driver.driverFor(stack, host.getClass)) match {
         case Some(driver: Processor) if driver.slot(stack) == Slot.CPU =>
           Option(driver.architecture(stack)) match {
             case Some(clazz) =>
-              if (oldArchitecture == null || oldArchitecture.getClass != clazz) {
-                architecture = clazz.getConstructor(classOf[machine.Machine]).newInstance(this)
-                if (node.network != null) architecture.onConnect()
+              if (architecture == null || architecture.getClass != clazz) {
+                newArchitecture = clazz.getConstructor(classOf[machine.Machine]).newInstance(this)
               }
               else {
-                architecture = oldArchitecture
+                newArchitecture = architecture
               }
               true
             case _ => false
@@ -138,6 +136,12 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
       }
       case _ => false
     }
+    // This needs to operate synchronized against the worker thread, to avoid the
+    // architecture changing while it is currently being executed.
+    if (newArchitecture != architecture) this.synchronized {
+      architecture = newArchitecture
+      if (architecture != null && node.network != null) architecture.onConnect()
+    }
     hasMemory = Option(architecture).fold(false)(_.recomputeMemory(components))
   }