diff --git a/src/api/java/appeng/api/crafting/ICraftingHelper.java b/src/api/java/appeng/api/crafting/ICraftingHelper.java
index 909f26353..b55c5caf8 100644
--- a/src/api/java/appeng/api/crafting/ICraftingHelper.java
+++ b/src/api/java/appeng/api/crafting/ICraftingHelper.java
@@ -53,6 +53,8 @@ public interface ICraftingHelper {
      * @param stack If null, a new item will be created to hold the encoded pattern.
      *              Otherwise the given item must already contains an encoded
      *              pattern that will be overwritten.
+     * @throws IllegalArgumentException If either in or out contain only empty
+     *                                  ItemStacks.
      * @return A new encoded pattern, or the given stack with the pattern encoded in
      *         it.
      */
@@ -73,6 +75,8 @@ public interface ICraftingHelper {
      *                         operation by the ME system.
      * @param allowSubstitutes Controls whether the ME system will allow the use of
      *                         equivalent items to craft this recipe.
+     * @throws IllegalArgumentException If either in or out contain only empty
+     *                                  ItemStacks.
      */
     ItemStack encodeCraftingPattern(@Nullable ItemStack stack, ICraftingRecipe recipe, ItemStack[] in, ItemStack out,
             boolean allowSubstitutes);
diff --git a/src/main/java/appeng/container/implementations/PatternTermContainer.java b/src/main/java/appeng/container/implementations/PatternTermContainer.java
index 23f8d579b..0898e52bc 100644
--- a/src/main/java/appeng/container/implementations/PatternTermContainer.java
+++ b/src/main/java/appeng/container/implementations/PatternTermContainer.java
@@ -261,13 +261,19 @@ public class PatternTermContainer extends MEMonitorableContainer
                 return new ItemStack[] { out };
             }
         } else {
+            boolean hasValue = false;
             final ItemStack[] list = new ItemStack[3];
 
             for (int i = 0; i < this.outputSlots.length; i++) {
                 final ItemStack out = this.outputSlots[i].getStack();
                 list[i] = out;
+                if (!out.isEmpty()) {
+                    hasValue = true;
+                }
+            }
+            if (hasValue) {
+                return list;
             }
-            return list;
         }
 
         return null;
diff --git a/src/main/java/appeng/core/api/ApiCrafting.java b/src/main/java/appeng/core/api/ApiCrafting.java
index e4f710bc2..b91888998 100644
--- a/src/main/java/appeng/core/api/ApiCrafting.java
+++ b/src/main/java/appeng/core/api/ApiCrafting.java
@@ -115,7 +115,12 @@ public class ApiCrafting implements ICraftingHelper {
         // We use the shared itemstack for an identity lookup.
         IAEItemStack ais = Api.instance().storage().getStorageChannel(IItemStorageChannel.class).createStack(is);
 
-        return new CraftingPatternDetails(ais, world);
+        try {
+            return new CraftingPatternDetails(ais, world);
+        } catch (IllegalStateException e) {
+            AELog.warn("Could not decode an invalid pattern %s: %s", is, e);
+            return null;
+        }
     }
 
     private boolean attemptRecovery(EncodedPatternItem patternItem, ItemStack itemStack, World world) {
diff --git a/src/main/java/appeng/items/misc/EncodedPatternItem.java b/src/main/java/appeng/items/misc/EncodedPatternItem.java
index d3e1e504e..e4734d8de 100644
--- a/src/main/java/appeng/items/misc/EncodedPatternItem.java
+++ b/src/main/java/appeng/items/misc/EncodedPatternItem.java
@@ -307,14 +307,27 @@ public class EncodedPatternItem extends AEBaseItem {
         final ListNBT tagIn = new ListNBT();
         final ListNBT tagOut = new ListNBT();
 
+        boolean hasInput = false;
         for (final ItemStack i : in) {
             tagIn.add(createItemTag(i));
+            if (!i.isEmpty()) {
+                hasInput = true;
+            }
         }
 
+        Preconditions.checkArgument(hasInput, "cannot encode a pattern that has no inputs.");
+
+        boolean hasNonEmptyOutput = false;
         for (final ItemStack i : out) {
             tagOut.add(createItemTag(i));
+            if (!i.isEmpty()) {
+                hasNonEmptyOutput = true;
+            }
         }
 
+        // Patterns without any outputs are corrupt! Never encode such a pattern.
+        Preconditions.checkArgument(hasNonEmptyOutput, "cannot encode a pattern that has no output.");
+
         encodedValue.put(EncodedPatternItem.NBT_INGREDIENTS, tagIn);
         encodedValue.put(EncodedPatternItem.NBT_PRODUCTS, tagOut);
         return encodedValue;