diff --git a/zkclient/settings.go b/zkclient/settings.go
index 89e7162..a86cbc6 100644
--- a/zkclient/settings.go
+++ b/zkclient/settings.go
@@ -298,7 +298,7 @@ func ObtainSettings() (*Settings, error) {
 		if err != nil {
 			return nil, fmt.Errorf("groups: %q: %v", group, err)
 		}
-		if n == 0 || n > len(groups)+1 {
+		if n <= 0 || n > len(groups)+1 {
 			return nil, fmt.Errorf("groups: %q: window %d unusable", group, n)
 		}
 		g := &openGroups[n-1]