diff --git a/projects/common/src/main/java/dan200/computercraft/shared/turtle/recipes/TurtleUpgradeRecipe.java b/projects/common/src/main/java/dan200/computercraft/shared/turtle/recipes/TurtleUpgradeRecipe.java
index 3ad657e47..8fc59ea06 100644
--- a/projects/common/src/main/java/dan200/computercraft/shared/turtle/recipes/TurtleUpgradeRecipe.java
+++ b/projects/common/src/main/java/dan200/computercraft/shared/turtle/recipes/TurtleUpgradeRecipe.java
@@ -111,7 +111,9 @@ public final class TurtleUpgradeRecipe extends CustomRecipe {
             itemTurtle.getUpgradeWithData(turtle, TurtleSide.RIGHT),
         };
 
-        // Get the upgrades for the new items
+        // Get the upgrades for the new items.
+        // Note: because the turtle is facing towards us, the directions are flipped. Items placed to the left
+        // of the turtle, are equipped on its right (and vice versa).
         var items = new ItemStack[]{ rightItem, leftItem };
         for (var i = 0; i < 2; i++) {
             if (!items[i].isEmpty()) {
diff --git a/projects/common/src/testFixtures/java/dan200/computercraft/test/shared/ItemStackMatcher.java b/projects/common/src/testFixtures/java/dan200/computercraft/test/shared/ItemStackMatcher.java
index dc6b50285..ace7d0cee 100644
--- a/projects/common/src/testFixtures/java/dan200/computercraft/test/shared/ItemStackMatcher.java
+++ b/projects/common/src/testFixtures/java/dan200/computercraft/test/shared/ItemStackMatcher.java
@@ -29,7 +29,7 @@ public class ItemStackMatcher extends TypeSafeMatcher<ItemStack> {
 
     @Override
     protected void describeMismatchSafely(ItemStack item, Description description) {
-        description.appendText("was ").appendValue(stack).appendValue(stack.getTag());
+        description.appendText("was ").appendValue(item).appendValue(item.getTag());
     }
 
     public static Matcher<ItemStack> isStack(ItemStack stack) {
diff --git a/projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Turtle_Test.kt b/projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Turtle_Test.kt
index 44a1a1755..c24126db2 100644
--- a/projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Turtle_Test.kt
+++ b/projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Turtle_Test.kt
@@ -29,6 +29,7 @@ import dan200.computercraft.shared.util.WaterloggableHelpers
 import dan200.computercraft.test.core.assertArrayEquals
 import dan200.computercraft.test.core.computer.LuaTaskContext
 import dan200.computercraft.test.core.computer.getApi
+import dan200.computercraft.test.shared.ItemStackMatcher.isStack
 import net.minecraft.core.BlockPos
 import net.minecraft.gametest.framework.GameTest
 import net.minecraft.gametest.framework.GameTestHelper
@@ -908,6 +909,83 @@ class Turtle_Test {
         thenWaitUntil { helper.assertContainerEmpty(BlockPos(2, 3, 2)) }
     }
 
+    /**
+     * Test that turtles can be crafted with upgrades.
+     */
+    @GameTest(template = Structures.DEFAULT)
+    fun Can_upgrades_be_crafted(helper: GameTestHelper) = helper.immediate {
+        fun turtle(left: UpgradeData<ITurtleUpgrade>? = null, right: UpgradeData<ITurtleUpgrade>? = null): ItemStack =
+            ModRegistry.Items.TURTLE_NORMAL.get()
+                .create(-1, null, -1, left, right, 0, null)
+
+        val pick = TurtleUpgrades.instance().get(ItemStack(Items.DIAMOND_PICKAXE))!!
+        val sword = TurtleUpgrades.instance().get(ItemStack(Items.DIAMOND_SWORD))!!
+
+        // Check we can craft with upgrades
+        assertThat(
+            "Craft with item on left equips on right",
+            helper.craftItem(
+                ItemStack(Items.DIAMOND_PICKAXE), turtle(), ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ),
+            isStack(turtle(right = pick)),
+        )
+        assertThat(
+            "Craft with item on right equips on left",
+            helper.craftItem(
+                ItemStack.EMPTY, turtle(), ItemStack(Items.DIAMOND_PICKAXE),
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ),
+            isStack(turtle(left = pick)),
+        )
+        assertThat(
+            "Craft with two items",
+            helper.craftItem(
+                ItemStack(Items.DIAMOND_SWORD), turtle(), ItemStack(Items.DIAMOND_PICKAXE),
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ),
+            isStack(turtle(left = pick, right = sword)),
+        )
+        assertThat(
+            "Maintains upgrades",
+            helper.craftItem(
+                ItemStack(Items.DIAMOND_SWORD), turtle(left = pick), ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+                ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ),
+            isStack(turtle(left = pick, right = sword)),
+        )
+
+        // Cannot craft when already have item
+        helper.assertNotCraftable(
+            ItemStack.EMPTY, turtle(left = sword), ItemStack(Items.DIAMOND_PICKAXE),
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+        )
+
+        // Cannot craft with an invalid upgrade
+        helper.assertNotCraftable(
+            ItemStack.EMPTY, turtle(), ItemStack(Items.DIRT),
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+        )
+
+        // Cannot craft with extra items in the inventory
+        helper.assertNotCraftable(
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack(Items.DIRT),
+            ItemStack.EMPTY, turtle(), ItemStack(Items.DIAMOND_PICKAXE),
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+        )
+        helper.assertNotCraftable(
+            ItemStack.EMPTY, turtle(), ItemStack(Items.DIAMOND_PICKAXE),
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack(Items.DIRT),
+            ItemStack.EMPTY, ItemStack.EMPTY, ItemStack.EMPTY,
+        )
+    }
+
     /**
      * Render turtles as an item.
      */