diff --git a/src/main/scala/li/cil/oc/common/component/TextBuffer.scala b/src/main/scala/li/cil/oc/common/component/TextBuffer.scala
index 7746fea92..16522b7b6 100644
--- a/src/main/scala/li/cil/oc/common/component/TextBuffer.scala
+++ b/src/main/scala/li/cil/oc/common/component/TextBuffer.scala
@@ -591,7 +591,7 @@ object TextBuffer {
     private lazy val Debugger = api.Items.get("debugger")
 
     private def debug(message: String) {
-      if (api.Items.get(Minecraft.getMinecraft.thePlayer.getHeldItem) == Debugger) {
+      if (Minecraft.getMinecraft != null && Minecraft.getMinecraft.thePlayer != null && api.Items.get(Minecraft.getMinecraft.thePlayer.getHeldItem) == Debugger) {
         OpenComputers.log.info(s"[NETWORK DEBUGGER] Sending packet to node $nodeAddress: " + message)
       }
     }
diff --git a/src/main/scala/li/cil/oc/common/tileentity/Robot.scala b/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
index 82a5e6f9f..a708b1609 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/Robot.scala
@@ -486,7 +486,20 @@ class Robot extends traits.Computer with traits.PowerInformation with IFluidHand
 
   override def markDirty() {
     super.markDirty()
-    updateInventorySize()
+    // Avoid getting into a bad state on the client when updating before we
+    // got the descriptor packet from the server. If we manage to open the
+    // GUI before the descriptor packet arrived, close it again because it is
+    // invalid anyway.
+    if (inventorySize >= 0) {
+      updateInventorySize()
+    }
+    else if (isClient) {
+      Minecraft.getMinecraft.currentScreen match {
+        case robotGui: gui.Robot if robotGui.robot == this =>
+          Minecraft.getMinecraft.displayGuiScreen(null)
+        case _ =>
+      }
+    }
     renderingErrored = false
   }
 
@@ -592,8 +605,9 @@ class Robot extends traits.Computer with traits.PowerInformation with IFluidHand
         setInventorySlotContents(slot, null)
         if (stack != null) removed += stack
       }
-      Array.copy(components, getSizeInventory - componentCount, components, realSize, componentCount)
-      for (slot <- getSizeInventory - componentCount until getSizeInventory if slot < realSize || slot >= realSize + componentCount) {
+      val copyComponentCount = math.min(getSizeInventory, componentCount)
+      Array.copy(components, getSizeInventory - copyComponentCount, components, realSize, copyComponentCount)
+      for (slot <- math.max(0, getSizeInventory - componentCount) until getSizeInventory if slot < realSize || slot >= realSize + componentCount) {
         components(slot) = None
       }
       getSizeInventory = realSize + componentCount