diff --git a/src/main/java/catering/inventory/ConsumableMutateForm.java b/src/main/java/catering/inventory/ConsumableMutateForm.java
index c41893a..b123661 100644
--- a/src/main/java/catering/inventory/ConsumableMutateForm.java
+++ b/src/main/java/catering/inventory/ConsumableMutateForm.java
@@ -48,7 +48,13 @@ class ConsumableMutateForm extends InventoryMutateForm {
 				getMetric());
 	}
 
-	public static ConsumableMutateForm of(Consumable product, UniqueInventoryItem item) {
+	public static ConsumableMutateForm of(UniqueInventoryItem item) {
+		Consumable product;
+		if (item.getProduct() instanceof Consumable consumable) {
+			product = consumable;
+		} else {
+			throw new IllegalArgumentException("Item must be for a product of type Consumable");
+		}
 		ConsumableMutateForm form = new ConsumableMutateForm();
 		form.setName(product.getName());
 		form.setQuantity(item.getQuantity().getAmount().longValueExact());
diff --git a/src/main/java/catering/inventory/InventoryController.java b/src/main/java/catering/inventory/InventoryController.java
index 06bee3b..c239f64 100644
--- a/src/main/java/catering/inventory/InventoryController.java
+++ b/src/main/java/catering/inventory/InventoryController.java
@@ -81,7 +81,7 @@ class InventoryController {
 	@GetMapping("/inventory/edit/{pid}")
 	String edit(Model model, @PathVariable Product pid) {
 		UniqueInventoryItem item = inventory.findByProduct(pid).get();
-		final InventoryMutateForm form = InventoryMutateForm.of(pid, item);
+		final InventoryMutateForm form = InventoryMutateForm.of(item);
 
 		return edit(model, form);
 	}
diff --git a/src/main/java/catering/inventory/InventoryMutateForm.java b/src/main/java/catering/inventory/InventoryMutateForm.java
index 5d6d724..a9c8f8e 100644
--- a/src/main/java/catering/inventory/InventoryMutateForm.java
+++ b/src/main/java/catering/inventory/InventoryMutateForm.java
@@ -111,13 +111,14 @@ abstract class InventoryMutateForm {
 	 * @param item an {@link UniqueInventoryItem} holding a {@link Quantity}
 	 * @return an object of an {@link InventoryMutateForm} subclass
 	 */
-	public static InventoryMutateForm of(Product product, UniqueInventoryItem item) {
-		if (product instanceof Consumable consumable) {
-			return ConsumableMutateForm.of(consumable, item);
-		} else if (product instanceof Rentable rentable) {
-			return RentableMutateForm.of(rentable, item);
+	public static InventoryMutateForm of(UniqueInventoryItem item) {
+		Product product = item.getProduct();
+		if (product instanceof Consumable) {
+			return ConsumableMutateForm.of(item);
+		} else if (product instanceof Rentable) {
+			return RentableMutateForm.of(item);
 		} else {
-			throw new IllegalArgumentException("InventoryMutateForm::ofProductAndItem not supported for given types");
+			throw new IllegalArgumentException("InventoryMutateForm::of not supported for given types");
 		}
 	}
 
diff --git a/src/main/java/catering/inventory/RentableMutateForm.java b/src/main/java/catering/inventory/RentableMutateForm.java
index 43884fc..88e2682 100644
--- a/src/main/java/catering/inventory/RentableMutateForm.java
+++ b/src/main/java/catering/inventory/RentableMutateForm.java
@@ -23,7 +23,13 @@ class RentableMutateForm extends InventoryMutateForm {
 		this.wholesalePrice = wholesalePrice;
 	}
 
-	public static RentableMutateForm of(Rentable product, UniqueInventoryItem item) {
+	public static RentableMutateForm of(UniqueInventoryItem item) {
+		Rentable product;
+		if (item.getProduct() instanceof Rentable rentable) {
+			product = rentable;
+		} else {
+			throw new IllegalArgumentException("Item must be for a product of type Rentable");
+		}
 		RentableMutateForm form = new RentableMutateForm();
 		form.setName(product.getName());
 		form.setQuantity(item.getQuantity().getAmount().longValueExact());