Should you repeat the salah if you forget a raka?

If I accidentally pray only 3 rakats for a 4 rakat Salah would I need to repeat the prayer

If you forget one of the essential parts of salah, such as a raka, and some time passes, and later you remember and know with certainty that your salah was deficient, then you must redo the salah.

References

Related fatwa from the Qatari Fatwa Authority (Arabic PDF)