diff --git a/src/classes/shopping_cart.ts b/src/classes/shopping_cart.ts
index 301e2755..d84993ff 100644
--- a/src/classes/shopping_cart.ts
+++ b/src/classes/shopping_cart.ts
@@ -178,9 +178,10 @@ export class ShoppingCart {
         this.cart.push(...optimumMatch);
         this.match.push({ ingredient, selection: optimumMatch });
       } catch (error) {
-        /* v8 ignore else -- @preserve */
         if (error instanceof NoProductMatchError) {
           this.misMatch.push({ ingredient, reason: error.reason });
+        } else {
+          throw error;
         }
       }
     }
diff --git a/src/utils/parser_helpers.ts b/src/utils/parser_helpers.ts
index 138ec279..263f5167 100644
--- a/src/utils/parser_helpers.ts
+++ b/src/utils/parser_helpers.ts
@@ -262,10 +262,11 @@ export function findAndUpsertCookware(
             quantity,
           );
         } catch (e) {
-          /* v8 ignore else -- expliciting error type -- @preserve */
           if (e instanceof CannotAddTextValueError) {
             diagnostics.push(createDiagnostic("COOKLANG_W0401", {}, span));
             return cookware.push(newCookware) - 1;
+          } else {
+            throw e;
           }
         }
       }
diff --git a/test/parser_helpers.test.ts b/test/parser_helpers.test.ts
index 9d57ef30..92a47fd1 100644
--- a/test/parser_helpers.test.ts
+++ b/test/parser_helpers.test.ts
@@ -922,6 +922,29 @@ describe("findAndUpsertCookware", () => {
     expect(diagnostics).toHaveDiagnostic("COOKLANG_W0401");
   });
 
+  it("should rethrow errors other than CannotAddTextValueError", () => {
+    const cookware: Cookware[] = [
+      {
+        name: "oven",
+        quantity: {
+          type: "fixed",
+          value: { type: "fraction", num: 1, den: 0 },
+        },
+      },
+    ];
+    const newCookware: Cookware = {
+      name: "oven",
+      quantity: {
+        type: "fixed",
+        value: { type: "fraction", num: 1, den: 1 },
+      },
+    };
+
+    expect(() => findAndUpsertCookware(cookware, newCookware, true)).toThrow(
+      DivisionByZeroError,
+    );
+  });
+
   it("should throw a ReferencedCookwareNotFoundError if a reference cookware does not exist", () => {
     const newCookware: Cookware = { name: "unreferenced-cookware", flags: [] };
     expect(() => findAndUpsertCookware([], newCookware, true, [])).toThrow(
diff --git a/test/shopping_cart.test.ts b/test/shopping_cart.test.ts
index 0c9ca801..c60d4ac3 100644
--- a/test/shopping_cart.test.ts
+++ b/test/shopping_cart.test.ts
@@ -106,6 +106,7 @@ describe("initialisation", () => {
       catalog: productCatalog,
       list: shoppingList,
     });
+
     expect(shoppingCart.productCatalog).toBe(productCatalog);
     expect(shoppingCart.shoppingList).toBe(shoppingList);
   });
@@ -127,6 +128,23 @@ describe("initialisation", () => {
   });
 });
 
+describe("unexpected matching errors", () => {
+  it("rethrows errors other than NoProductMatchError", () => {
+    const shoppingList = new ShoppingList();
+    shoppingList.addRecipe(new Recipe("@flour{1%g}"));
+    const shoppingCart = new ShoppingCart({
+      catalog: productCatalog,
+      list: shoppingList,
+    });
+    const unexpected = new Error("Unexpected matching failure");
+    Reflect.set(shoppingCart, "getOptimumMatch", () => {
+      throw unexpected;
+    });
+
+    expect(() => shoppingCart.buildCart()).toThrow(unexpected);
+  });
+});
+
 describe("buildCart", () => {
   it("should handle ingredients with no matching products", () => {
     const shoppingCart = new ShoppingCart();