diff --git a/app/vmselect/netstorage/netstorage.go b/app/vmselect/netstorage/netstorage.go
index 937628c8f..3c4e00796 100644
--- a/app/vmselect/netstorage/netstorage.go
+++ b/app/vmselect/netstorage/netstorage.go
@@ -234,7 +234,7 @@ func (pts *packedTimeseries) Unpack(tbf *tmpBlocksFile, dst *Result, tr storage.
 		}
 		if firstErr == nil {
 			sbs = append(sbs, upw.sb)
-		} else {
+		} else if upw.sb != nil {
 			putSortBlock(upw.sb)
 		}
 	}