diff --git a/src/main/scala/li/cil/oc/server/component/UpgradeCrafting.scala b/src/main/scala/li/cil/oc/server/component/UpgradeCrafting.scala
index 7d0d47006..b6f00581c 100644
--- a/src/main/scala/li/cil/oc/server/component/UpgradeCrafting.scala
+++ b/src/main/scala/li/cil/oc/server/component/UpgradeCrafting.scala
@@ -56,11 +56,14 @@ class UpgradeCrafting(val host: EnvironmentHost with internal.Robot) extends pre
       load()
       val cm = CraftingManager.getInstance
       var countCrafted = 0
-      val canCraft = cm.findMatchingRecipe(CraftingInventory, host.world) != null
+      val originalCraft = cm.findMatchingRecipe(CraftingInventory, host.world)
       breakable {
         while (countCrafted < wantedCount) {
           val result = cm.findMatchingRecipe(CraftingInventory, host.world)
           if (result == null || result.stackSize < 1) break()
+          if (!originalCraft.isItemEqual(result)) {
+            break()
+          }
           countCrafted += result.stackSize
           FMLCommonHandler.instance.firePlayerCraftingEvent(host.player, result, this)
           val surplus = mutable.ArrayBuffer.empty[ItemStack]
@@ -91,7 +94,7 @@ class UpgradeCrafting(val host: EnvironmentHost with internal.Robot) extends pre
           load()
         }
       }
-      Seq(canCraft, countCrafted)
+      Seq(originalCraft != null, countCrafted)
     }
 
     def load() {
diff --git a/src/main/scala/li/cil/oc/server/machine/luac/ComputerAPI.scala b/src/main/scala/li/cil/oc/server/machine/luac/ComputerAPI.scala
index f66693a5c..6404f85b3 100644
--- a/src/main/scala/li/cil/oc/server/machine/luac/ComputerAPI.scala
+++ b/src/main/scala/li/cil/oc/server/machine/luac/ComputerAPI.scala
@@ -77,15 +77,18 @@ class ComputerAPI(owner: NativeLuaArchitecture) extends NativeLuaAPI(owner) {
     })
     lua.setField(-2, "users")
 
-    lua.pushScalaFunction(lua => try {
-      machine.addUser(lua.checkString(1))
-      lua.pushBoolean(true)
-      1
-    } catch {
-      case e: Throwable =>
-        lua.pushNil()
-        lua.pushString(Option(e.getMessage).getOrElse(e.toString))
-        2
+    lua.pushScalaFunction(lua => {
+      val user = lua.checkString(1)
+      try {
+        machine.addUser(user)
+        lua.pushBoolean(true)
+        1
+      } catch {
+        case e: Throwable =>
+          lua.pushNil()
+          lua.pushString(Option(e.getMessage).getOrElse(e.toString))
+          2
+      }
     })
     lua.setField(-2, "addUser")