diff --git a/src/main/java/appeng/client/gui/AEBaseGui.java b/src/main/java/appeng/client/gui/AEBaseGui.java
index 5dc7e33d1..6334712cf 100644
--- a/src/main/java/appeng/client/gui/AEBaseGui.java
+++ b/src/main/java/appeng/client/gui/AEBaseGui.java
@@ -64,7 +64,7 @@ import appeng.client.me.SlotME;
 import appeng.client.render.StackSizeRenderer;
 import appeng.container.AEBaseContainer;
 import appeng.container.slot.*;
-import appeng.container.slot.AppEngSlot.hasCalculatedValidness;
+import appeng.container.slot.AppEngSlot.CalculatedValidity;
 import appeng.core.AELog;
 import appeng.core.AppEng;
 import appeng.core.sync.network.NetworkHandler;
@@ -701,7 +701,8 @@ public abstract class AEBaseGui<T extends AEBaseContainer> extends ContainerScre
                 }
 
                 if (!is.isEmpty() && s instanceof AppEngSlot) {
-                    if (((AppEngSlot) s).getIsValid() == hasCalculatedValidness.NotAvailable) {
+                    AppEngSlot aeSlot = (AppEngSlot) s;
+                    if (aeSlot.getIsValid() == CalculatedValidity.NotAvailable) {
                         boolean isValid = s.isItemValid(is) || s instanceof SlotOutput
                                 || s instanceof AppEngCraftingSlot || s instanceof SlotDisabled
                                 || s instanceof SlotInaccessible || s instanceof SlotFake
@@ -713,11 +714,10 @@ public abstract class AEBaseGui<T extends AEBaseContainer> extends ContainerScre
                                 AELog.debug(err);
                             }
                         }
-                        ((AppEngSlot) s)
-                                .setIsValid(isValid ? hasCalculatedValidness.Valid : hasCalculatedValidness.Invalid);
+                        aeSlot.setIsValid(isValid ? CalculatedValidity.Valid : CalculatedValidity.Invalid);
                     }
 
-                    if (((AppEngSlot) s).getIsValid() == hasCalculatedValidness.Invalid) {
+                    if (aeSlot.getIsValid() == CalculatedValidity.Invalid) {
                         setBlitOffset(100);
                         this.itemRenderer.zLevel = 100.0F;
 
diff --git a/src/main/java/appeng/container/implementations/ContainerMolecularAssembler.java b/src/main/java/appeng/container/implementations/ContainerMolecularAssembler.java
index c63cd0be3..c6224e970 100644
--- a/src/main/java/appeng/container/implementations/ContainerMolecularAssembler.java
+++ b/src/main/java/appeng/container/implementations/ContainerMolecularAssembler.java
@@ -21,6 +21,7 @@ package appeng.container.implementations;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.player.PlayerInventory;
 import net.minecraft.inventory.container.ContainerType;
+import net.minecraft.inventory.container.Slot;
 import net.minecraft.item.ItemStack;
 import net.minecraft.network.PacketBuffer;
 import net.minecraft.world.World;
@@ -33,6 +34,7 @@ import appeng.api.networking.crafting.ICraftingPatternDetails;
 import appeng.container.ContainerLocator;
 import appeng.container.guisync.GuiSync;
 import appeng.container.interfaces.IProgressProvider;
+import appeng.container.slot.AppEngSlot;
 import appeng.container.slot.SlotMolecularAssemblerPattern;
 import appeng.container.slot.SlotOutput;
 import appeng.container.slot.SlotRestrictedInput;
@@ -60,6 +62,8 @@ public class ContainerMolecularAssembler extends ContainerUpgradeable implements
     @GuiSync(4)
     public int craftProgress = 0;
 
+    private Slot encodedPatternSlot;
+
     public ContainerMolecularAssembler(int id, final PlayerInventory ip, final TileMolecularAssembler te) {
         super(TYPE, id, ip, te);
         this.tma = te;
@@ -108,8 +112,9 @@ public class ContainerMolecularAssembler extends ContainerUpgradeable implements
         offX = 126;
         offY = 16;
 
-        this.addSlot(new SlotRestrictedInput(SlotRestrictedInput.PlacableItemType.ENCODED_CRAFTING_PATTERN, mac, 10,
-                offX, offY, this.getPlayerInventory()));
+        encodedPatternSlot = this
+                .addSlot(new SlotRestrictedInput(SlotRestrictedInput.PlacableItemType.ENCODED_CRAFTING_PATTERN, mac, 10,
+                        offX, offY, this.getPlayerInventory()));
         this.addSlot(new SlotOutput(mac, 9, offX, offY + 32, -1));
 
         offX = 122;
@@ -161,4 +166,19 @@ public class ContainerMolecularAssembler extends ContainerUpgradeable implements
     public int getMaxProgress() {
         return MAX_CRAFT_PROGRESS;
     }
+
+    @Override
+    public void onSlotChange(Slot s) {
+
+        // If the pattern changes, the crafting grid slots lose validity
+        if (s == encodedPatternSlot) {
+            for (Slot otherSlot : inventorySlots) {
+                if (otherSlot != s && otherSlot instanceof AppEngSlot) {
+                    ((AppEngSlot) otherSlot).setIsValid(AppEngSlot.CalculatedValidity.NotAvailable);
+                }
+            }
+        }
+
+    }
+
 }
diff --git a/src/main/java/appeng/container/slot/AppEngSlot.java b/src/main/java/appeng/container/slot/AppEngSlot.java
index df1018fe7..7daf8d83f 100644
--- a/src/main/java/appeng/container/slot/AppEngSlot.java
+++ b/src/main/java/appeng/container/slot/AppEngSlot.java
@@ -43,7 +43,7 @@ public class AppEngSlot extends Slot {
     private boolean isPlayerSide = false;
     private AEBaseContainer myContainer = null;
     private int IIcon = -1;
-    private hasCalculatedValidness isValid;
+    private CalculatedValidity isValid;
     private boolean isDisplay = false;
 
     public AppEngSlot(final IItemHandler inv, final int idx, final int x, final int y) {
@@ -53,7 +53,7 @@ public class AppEngSlot extends Slot {
 
         this.defX = x;
         this.defY = y;
-        this.setIsValid(hasCalculatedValidness.NotAvailable);
+        this.setIsValid(CalculatedValidity.NotAvailable);
     }
 
     public Slot setNotDraggable() {
@@ -105,10 +105,13 @@ public class AppEngSlot extends Slot {
     public void putStack(final ItemStack stack) {
         if (this.isSlotEnabled()) {
             ItemHandlerUtil.setStackInSlot(this.itemHandler, this.index, stack);
+            this.onSlotChanged();
+        }
+    }
 
-            if (this.getContainer() != null) {
-                this.getContainer().onSlotChange(this);
-            }
+    private void notifyContainerSlotChanged() {
+        if (this.getContainer() != null) {
+            this.getContainer().onSlotChange(this);
         }
     }
 
@@ -118,7 +121,9 @@ public class AppEngSlot extends Slot {
 
     @Override
     public void onSlotChanged() {
-        this.setIsValid(hasCalculatedValidness.NotAvailable);
+        super.onSlotChanged();
+        this.setIsValid(CalculatedValidity.NotAvailable);
+        notifyContainerSlotChanged();
     }
 
     @Override
@@ -220,11 +225,11 @@ public class AppEngSlot extends Slot {
         this.isPlayerSide = isPlayerSide;
     }
 
-    public hasCalculatedValidness getIsValid() {
+    public CalculatedValidity getIsValid() {
         return this.isValid;
     }
 
-    public void setIsValid(final hasCalculatedValidness isValid) {
+    public void setIsValid(final CalculatedValidity isValid) {
         this.isValid = isValid;
     }
 
@@ -236,7 +241,7 @@ public class AppEngSlot extends Slot {
         this.myContainer = myContainer;
     }
 
-    public enum hasCalculatedValidness {
+    public enum CalculatedValidity {
         NotAvailable, Valid, Invalid
     }
 }