diff --git a/cmd/mtwebmapper/tilesupdater.go b/cmd/mtwebmapper/tilesupdater.go
index 11df3c3..ab1690e 100644
--- a/cmd/mtwebmapper/tilesupdater.go
+++ b/cmd/mtwebmapper/tilesupdater.go
@@ -100,7 +100,7 @@ func (tu *tileUpdater) doUpdates() {
 		jobs := make(chan xz)
 		var done sync.WaitGroup
 
-		for i := 0; i < tu.workers; i++ {
+		for i, n := 0, min(tu.workers, len(changes)); i < n; i++ {
 			var client *common.RedisClient
 			var err error
 			if client, err = common.NewRedisClient("tcp", tu.redisAddress); err != nil {