diff --git a/cmd/mtwebmapper/main.go b/cmd/mtwebmapper/main.go
index 0465733..e80b5a8 100644
--- a/cmd/mtwebmapper/main.go
+++ b/cmd/mtwebmapper/main.go
@@ -76,7 +76,7 @@ func main() {
 	flag.StringVar(&playersFIFO, "ps", "", "Path to FIFO file to read active players from (shorthand).")
 	flag.IntVar(&yMin, "ymin", common.MinHeight, "Minimum y in blocks.")
 	flag.IntVar(&yMax, "ymax", common.MaxHeight, "Maximum y in blocks.")
-	flag.CommandLine.DurationVar(&changeDuration, "change-duration", time.Second, "Duration to aggregate changes. (PG only)")
+	flag.DurationVar(&changeDuration, "change-duration", time.Second, "Duration to aggregate changes. (PG only)")
 	flag.BoolVar(&version, "version", false, "Print version and exit.")
 
 	flag.Parse()