diff --git a/.gitignore b/.gitignore
index e3882f7..5e8ec3a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,5 +4,5 @@
 *.swp
 *.swo
 *.orig
-
+.DS_Store
 dist/
diff --git a/internal/mergequeue/coordinator.go b/internal/mergequeue/coordinator.go
index 30e2cee..b757c27 100644
--- a/internal/mergequeue/coordinator.go
+++ b/internal/mergequeue/coordinator.go
@@ -432,6 +432,13 @@ func (a *Coordinator) processPullRequestEvent(ctx context.Context, logger *zap.L
 			)
 			return
 		}
+		// If pr == nil, it means that the queue has already been deleted earlier by another event.
+		if pr == nil {
+			logger.Warn(
+				"PR already dequeued or queue non-existent",
+			)
+			return
+		}
 
 		if ev.PullRequest.GetMerged() {
 			metrics.RecordTimeToMerge(time.Since(pr.EnqueuedAt), owner, repo)
@@ -926,6 +933,10 @@ func (a *Coordinator) Dequeue(_ context.Context, baseBranch *BaseBranch, prNumbe
 
 	pr, err := q.Dequeue(prNumber, setPendingStatusState)
 	if err != nil {
+		// If there is a queue but no PR in it, this may also be a duplicate.
+		if errors.Is(err, ErrNotFound) {
+			return nil, nil
+		}
 		return nil, fmt.Errorf("removing pr from merge queue failed: %w", err)
 	}