diff --git a/pyconfr-to-mastodon.py b/pyconfr-to-mastodon.py
index 179f9ff..c1a85fd 100644
--- a/pyconfr-to-mastodon.py
+++ b/pyconfr-to-mastodon.py
@@ -144,6 +144,9 @@ def live_toot(talks, mastodon: Mastodon, ahead_days=0):
         delta = (
             talk.start_date - datetime.now(timezone.utc) - timedelta(days=ahead_days)
         )
+        if delta.total_seconds() < -300:
+            logging.info("Skipping %s (already happened).", talk.title)
+            continue
         if delta.total_seconds() > 10:
             logging.info("Waiting %s for %s to start.", delta, talk.title)
             sleep(delta.total_seconds() - 2)  # Wait for the talk to start.