diff --git a/server/internal/database/replication_slot_advance_from_cts_resource.go b/server/internal/database/replication_slot_advance_from_cts_resource.go
index 4b3fb710..48bb324b 100644
--- a/server/internal/database/replication_slot_advance_from_cts_resource.go
+++ b/server/internal/database/replication_slot_advance_from_cts_resource.go
@@ -133,9 +133,11 @@ func (r *ReplicationSlotAdvanceFromCTSResource) Create(ctx context.Context, rc *
 		return fmt.Errorf("failed to query target replication slot lsn: %w", err)
 	}
 
-	if targetLSN <= currentLSN {
-		// No need to advance if the slot is already ahead of the commit
-		// timestamp
+	atOrBefore, err := postgres.LsnAtOrBefore(targetLSN, currentLSN).Scalar(ctx, conn)
+	if err != nil {
+		return fmt.Errorf("failed to compare LSNs: %w", err)
+	}
+	if atOrBefore {
 		return nil
 	}
 
diff --git a/server/internal/postgres/create_db.go b/server/internal/postgres/create_db.go
index cd6e0107..5a52bb2b 100644
--- a/server/internal/postgres/create_db.go
+++ b/server/internal/postgres/create_db.go
@@ -448,6 +448,16 @@ func SpockProgressReachedLSN(peerNodeName, targetLSN string) Query[bool] {
 	}
 }
 
+// LsnAtOrBefore reports whether lsn1 <= lsn2 using PostgreSQL's pg_lsn type.
+// Use this instead of Go string comparison — LSNs are hex-formatted and string
+// ordering produces wrong results across segment boundaries (e.g. "F/..." > "10/...").
+func LsnAtOrBefore(lsn1, lsn2 string) Query[bool] {
+	return Query[bool]{
+		SQL:  "SELECT @lsn1::pg_lsn <= @lsn2::pg_lsn",
+		Args: pgx.NamedArgs{"lsn1": lsn1, "lsn2": lsn2},
+	}
+}
+
 // GetSubscriptionStatus returns the current status of a specific subscription
 func GetSubscriptionStatus(providerNode, subscriberNode string) Query[string] {
 	return Query[string]{