diff --git a/Ceph/Script/queryCephDisks.pl b/Ceph/Script/queryCephDisks.pl
index 1d947e6a9ee674731655e3dbbb34427f1dfdbee1..242247951b17c9616345ff79322d1cf547f94f36 100755
--- a/Ceph/Script/queryCephDisks.pl
+++ b/Ceph/Script/queryCephDisks.pl
@@ -132,7 +132,7 @@ if (defined $opt_select) {
 	$selectSize += 0.;
     }
 }
-unless ($selectSizeOrDev and $selectSize >= 0.) {
+if ($selectSizeOrDev > 0 and $selectSize < 0.) {
     fail_usage "SelectSize option -s expects positive float, when used together with -p option.";
 }
 #