diff --git a/cmd/mbf/main.go b/cmd/mbf/main.go
index c382144..593228c 100644
--- a/cmd/mbf/main.go
+++ b/cmd/mbf/main.go
@@ -62,10 +62,13 @@ func main() {
 			return
 		}
 		if cache, err = pkg.Open(ctx, msg, flagCures, base); err == nil {
-			if flagTShift < 0 || flagTShift > 31 {
-				flagTShift = 31
+			if flagTShift < 0 {
+				cache.SetThreshold(0)
+			} else if flagTShift > 31 {
+				cache.SetThreshold(1 << 31)
+			} else {
+				cache.SetThreshold(1 << flagTShift)
 			}
-			cache.SetThreshold(1 << flagTShift)
 		}
 		return
 	}).Flag(