diff --git a/src/utils/importFormat.test.ts b/src/utils/importFormat.test.ts
index 0026c7c..8e450ae 100644
--- a/src/utils/importFormat.test.ts
+++ b/src/utils/importFormat.test.ts
@@ -416,6 +416,35 @@ describe("mapRow — debit/credit is a subtraction, not a nullity test (#325)",
     ).toBe(60);
   });
 
+  it("errors on an unreadable cell even when its sibling parses", () => {
+    // The review finding on #336: testing `isNaN(debit) && isNaN(credit)` only
+    // caught the case where BOTH sides fell. But the unused column carries
+    // `0,00` in exactly the files this rule exists to fix, so an unreadable
+    // debit beside a `0,00` credit computed 0 − 0 = 0 and imported silently —
+    // the very bug, one cell over.
+    expect(
+      outcome(mapRow(["05/01/2025", "EPICERIE", "n/a", "0,00"], DC_FORMAT))
+    ).toBe(ROW_ERROR_KEYS.invalidAmount);
+    expect(
+      outcome(mapRow(["05/01/2025", "EPICERIE", "84,32 CAD", "0,00"], DC_FORMAT))
+    ).toBe(ROW_ERROR_KEYS.invalidAmount);
+    // Symmetric: an unreadable credit beside a readable debit.
+    expect(
+      outcome(mapRow(["15/01/2025", "PAIE", "0,00", "1 250 $ CAD"], DC_FORMAT))
+    ).toBe(ROW_ERROR_KEYS.invalidAmount);
+  });
+
+  it("still treats an EMPTY cell as absent, not as unreadable", () => {
+    // The distinction the fix rests on: empty means "this column does not apply
+    // to this row", which is the normal shape of a debit/credit file.
+    expect(
+      outcome(mapRow(["05/01/2025", "EPICERIE", "84,32", ""], DC_FORMAT))
+    ).toBe(-84.32);
+    expect(
+      outcome(mapRow(["05/01/2025", "EPICERIE", "84,32", "   "], DC_FORMAT))
+    ).toBe(-84.32);
+  });
+
   it("errors when NEITHER column is readable, instead of importing 0", () => {
     expect(outcome(mapRow(["05/01/2025", "X", "", ""], DC_FORMAT))).toBe(
       ROW_ERROR_KEYS.invalidAmount
diff --git a/src/utils/importFormat.ts b/src/utils/importFormat.ts
index 15cdc9c..7bbd836 100644
--- a/src/utils/importFormat.ts
+++ b/src/utils/importFormat.ts
@@ -277,8 +277,12 @@ export interface MapRowOptions {
  * convention (both columns hold positive numbers) even when an export negates
  * its debits.
  *
- * A row whose amount is unreadable in BOTH columns is an error, never a 0: an
- * amount nobody could read must not enter the ledger as a free transaction.
+ * A mapped cell that is NOT EMPTY but does not parse is an error, whatever its
+ * sibling holds. Testing `isNaN(debit) && isNaN(credit)` was not enough: the
+ * unused column carries `0,00` in exactly the files this rule exists to fix, so
+ * an unreadable debit beside a `0,00` credit parsed as 0 − 0 = 0 and imported
+ * silently — the very bug, one cell over. An EMPTY cell is different: it means
+ * the column does not apply to this row, and contributes zero.
  */
 export function mapRow(
   raw: string[],
@@ -304,6 +308,22 @@ export function mapRow(
       decimalSeparator: options.decimalSeparators?.get(col),
     });
 
+  /**
+   * Read one side of a debit/credit pair. `present` separates "the column does
+   * not apply to this row" (empty cell, contributes zero) from "the column says
+   * something we cannot read" (an error) — a distinction `isNaN` alone cannot
+   * make once the other side parses.
+   */
+  const readSide = (
+    col: number | undefined
+  ): { present: boolean; readable: boolean; value: number } => {
+    if (col === undefined) return { present: false, readable: true, value: 0 };
+    const text = raw[col]?.trim() ?? "";
+    if (!text) return { present: false, readable: true, value: 0 };
+    const value = readAmount(col);
+    return { present: true, readable: !isNaN(value), value };
+  };
+
   // 1. Configuration. An unmapped amount column used to fall back to `?? 0`,
   //    reading column 0 — usually the date — for every row of the file. That is
   //    a format error affecting the whole import, so it is reported before any
@@ -325,14 +345,20 @@ export function mapRow(
   // 3. Amount.
   let amount: number;
   if (format.amountMode === "debit_credit") {
-    const debit = debitMapped ? readAmount(mapping.debitAmount!) : NaN;
-    const credit = creditMapped ? readAmount(mapping.creditAmount!) : NaN;
-    if (isNaN(debit) && isNaN(credit)) {
+    const debit = readSide(debitMapped ? mapping.debitAmount : undefined);
+    const credit = readSide(creditMapped ? mapping.creditAmount : undefined);
+    // A cell that holds something we cannot read fails the row even when its
+    // sibling parses — otherwise the `0,00` filler silently answers for it.
+    if (!debit.readable || !credit.readable) {
+      return fail(ROW_ERROR_KEYS.invalidAmount);
+    }
+    // Both empty: the row states no amount at all.
+    if (!debit.present && !credit.present) {
       return fail(ROW_ERROR_KEYS.invalidAmount);
     }
     amount =
-      (isNaN(credit) ? 0 : Math.abs(credit)) -
-      (isNaN(debit) ? 0 : Math.abs(debit));
+      (credit.present ? Math.abs(credit.value) : 0) -
+      (debit.present ? Math.abs(debit.value) : 0);
   } else {
     amount = readAmount(mapping.amount!);
     if (isNaN(amount)) return fail(ROW_ERROR_KEYS.invalidAmount);