diff --git a/src/nlp/totext.ts b/src/nlp/totext.ts
index 1e0abac4..4a49e529 100644
--- a/src/nlp/totext.ts
+++ b/src/nlp/totext.ts
@@ -76,6 +76,9 @@ export default class ToText {
       const byweekday = !isArray(this.origOptions.byweekday)
         ? [this.origOptions.byweekday]
         : this.origOptions.byweekday
+      if(this.origOptions.bysetpos){
+        byweekday.forEach((weekday: Weekday) => weekday.nth(Number(this.origOptions.bysetpos)))
+      }
       const days = String(byweekday)
 
       this.byweekday = {
diff --git a/test/nlp.test.ts b/test/nlp.test.ts
index d53c6785..b408dea0 100644
--- a/test/nlp.test.ts
+++ b/test/nlp.test.ts
@@ -24,6 +24,7 @@ const texts = [
   ['Every month on the 3rd Tuesday', 'RRULE:FREQ=MONTHLY;BYDAY=+3TU'],
   ['Every month on the 3rd last Tuesday', 'RRULE:FREQ=MONTHLY;BYDAY=-3TU'],
   ['Every month on the last Monday', 'RRULE:FREQ=MONTHLY;BYDAY=-1MO'],
+  ['Every month on the last Monday', 'RRULE:FREQ=MONTHLY;BYDAY=MO;BYSETPOS=-1'],
   ['Every month on the 2nd last Friday', 'RRULE:FREQ=MONTHLY;BYDAY=-2FR'],
   // ['Every week until January 1, 2007', 'RRULE:FREQ=WEEKLY;UNTIL=20070101T080000Z'],
   ['Every week for 20 times', 'RRULE:FREQ=WEEKLY;COUNT=20']