diff --git a/src/base/match.cc b/src/base/match.cc
index 7c2c0cf58d..bfbdbf0b11 100644
--- a/src/base/match.cc
+++ b/src/base/match.cc
@@ -109,7 +109,7 @@ std::vector<std::vector<std::string> >
 ObjectMatch::getExpressions()
 {
     std::vector<std::vector<std::string> > to_return;
-    for (const std::vector<std::string> expression : tokens) {
+    for (const auto &expression: tokens) {
         std::vector<std::string> to_add;
         to_add.insert(to_add.end(), expression.begin(), expression.end());
         to_return.push_back(to_add);