diff --git a/src/to-human.ts b/src/to-human.ts
index 855efc3..5d7ccd5 100644
--- a/src/to-human.ts
+++ b/src/to-human.ts
@@ -154,9 +154,9 @@ export function toHuman(expression: string): string {
   if (parts.length !== 5 && parts.length !== 6) {
     throw new CronTranslateError(`Expected a 5- or 6-field cron expression, got ${parts.length} fields.`);
   }
-  const [sec, min, hour, dom, monthRaw, dowRaw] = parts.length === 6
-    ? parts
-    : ['0', ...parts];
+  // `?` (Quartz "no specific value") means no constraint on the field, same as `*`.
+  const fields = (parts.length === 6 ? parts : ['0', ...parts]).map((f) => (f === '?' ? '*' : f));
+  const [sec, min, hour, dom, monthRaw, dowRaw] = fields;
   const month = mapNames(monthRaw, MONTH_NUMS);
   const dow = mapNames(dowRaw, DOW_NUMS);
 
diff --git a/test/to-human.test.ts b/test/to-human.test.ts
index 3c1e3d2..91f7ec9 100644
--- a/test/to-human.test.ts
+++ b/test/to-human.test.ts
@@ -69,6 +69,17 @@ describe('toHuman — accepts month/weekday names in input', () => {
   });
 });
 
+describe('toHuman — treats ? (Quartz no-value) like *', () => {
+  const cases: [string, string][] = [
+    ['0 0 9 ? * MON', 'at 9am on monday'],
+    ['0 0 9 15 * ?', 'at 9am on day 15'],
+    ['0 0 0 ? * 1-5', 'on monday to friday'],
+  ];
+  it.each(cases)('%s => %s', (cron, expected) => {
+    expect(toHuman(cron)).toBe(expected);
+  });
+});
+
 describe('toHuman — rejects malformed input', () => {
   it.each(['', 'a b c', '1 2 3 4 5 6 7'])('rejects %j', (bad) => {
     expect(() => toHuman(bad)).toThrow();