diff --git a/CHANGELOG.md b/CHANGELOG.md
index c09994929..f491a4b7f 100755
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ### 1.6.6
 - Added new Crafter modes: ignore redstone signal, redstone signal unlocks autocrafting, redstone signal locks autocrafting and redstone pulse inserts next set (replacement for blocking mode) (raoulvdberge)
+- Fixed an autocrafting bug where it crashed when external inventories couldn't be filled (raoulvdberge)
 
 ### 1.6.5
 - Fixed Refined Storage silicon's oredict entry being registered too late (raoulvdberge)
diff --git a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/autocrafting/task/CraftingTask.java b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/autocrafting/task/CraftingTask.java
index a375a2c0d..434ac91fb 100755
--- a/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/autocrafting/task/CraftingTask.java
+++ b/src/main/java/com/raoulvdberge/refinedstorage/apiimpl/autocrafting/task/CraftingTask.java
@@ -32,6 +32,8 @@ import net.minecraft.world.World;
 import net.minecraftforge.common.util.Constants;
 import net.minecraftforge.fluids.FluidStack;
 import net.minecraftforge.items.ItemHandlerHelper;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 
 import javax.annotation.Nullable;
 import java.util.*;
@@ -57,6 +59,8 @@ public class CraftingTask implements ICraftingTask {
 
     private static final long CALCULATION_TIMEOUT_MS = 5000;
 
+    private static final Logger LOGGER = LogManager.getLogger();
+
     private INetwork network;
     private ICraftingRequestInfo requested;
     private int quantity;
@@ -687,28 +691,60 @@ public class CraftingTask implements ICraftingTask {
                     }
 
                     if (p.getState() == ProcessingState.READY && hasAll) {
-                        for (ItemStack need : p.getItemsToPut()) {
+                        boolean abort = false;
+
+                        for (int i = 0; i < p.getItemsToPut().size(); ++i) {
+                            ItemStack need = p.getItemsToPut().get(i);
+
                             ItemStack result = this.internalStorage.extract(need, need.getCount(), getFlags(need), Action.PERFORM);
                             if (result == null || result.getCount() != need.getCount()) {
-                                throw new IllegalStateException("Could not extract from the internal inventory even though we could");
+                                throw new IllegalStateException("The internal crafting inventory reported that " + need + " was available but we got " + result);
                             }
 
-                            if (!ItemHandlerHelper.insertItem(p.getPattern().getContainer().getConnectedInventory(), result, false).isEmpty()) {
-                                throw new IllegalStateException("Can't fill up inventory even though we could");
+                            ItemStack remainder = ItemHandlerHelper.insertItem(p.getPattern().getContainer().getConnectedInventory(), result, false);
+                            if (!remainder.isEmpty()) {
+                                LOGGER.warn("In a simulation, " + p.getPattern().getContainer().getConnectedInventory() + " reported that we could insert " + result + " but we got " + remainder + " as a remainder");
+
+                                this.internalStorage.insert(remainder, remainder.getCount(), Action.PERFORM);
+
+                                p.getItemsToPut().set(i, remainder);
+
+                                abort = true;
+
+                                break;
                             }
                         }
 
-                        for (FluidStack need : p.getFluidsToPut()) {
+                        if (abort) {
+                            continue;
+                        }
+
+                        for (int i = 0; i < p.getFluidsToPut().size(); ++i) {
+                            FluidStack need = p.getFluidsToPut().get(i);
+
                             FluidStack result = this.internalFluidStorage.extract(need, need.amount, IComparer.COMPARE_NBT, Action.PERFORM);
                             if (result == null || result.amount != need.amount) {
-                                throw new IllegalStateException("Could not extract from the internal inventory even though we could");
+                                throw new IllegalStateException("The internal crafting inventory reported that " + need + " was available but we got " + result);
                             }
 
-                            if (p.getPattern().getContainer().getConnectedFluidInventory().fill(result, true) != result.amount) {
-                                throw new IllegalStateException("Can't fill up inventory even though we could");
+                            int filled = p.getPattern().getContainer().getConnectedFluidInventory().fill(result, true);
+                            if (filled != result.amount) {
+                                LOGGER.warn("In a simulation, " + p.getPattern().getContainer().getConnectedFluidInventory() + " reported that we could fill " + result + " but we only filled " + filled);
+
+                                this.internalFluidStorage.insert(result, result.amount - filled, Action.PERFORM);
+
+                                p.getFluidsToPut().set(i, StackUtils.copy(result, result.amount - filled));
+
+                                abort = true;
+
+                                break;
                             }
                         }
 
+                        if (abort) {
+                            continue;
+                        }
+
                         p.setState(ProcessingState.EXTRACTED_ALL);
 
                         p.getPattern().getContainer().onUsedForProcessing();