diff --git a/store.go b/store.go
index d3d90ce..515a324 100644
--- a/store.go
+++ b/store.go
@@ -52,7 +52,7 @@ func (s *store) ensureOffset(offset int) {
 	}
 
 	s.match = s.match[:cap(s.match)]
-	for i := cap(s.match); i <= offset; i++ {
+	for i := len(s.match); i <= offset; i++ {
 		s.match = append(s.match, nil)
 	}
 }