diff --git a/tools/aapt2/ResourceUtils.cpp b/tools/aapt2/ResourceUtils.cpp
index 82d9e04..99420de 100644
--- a/tools/aapt2/ResourceUtils.cpp
+++ b/tools/aapt2/ResourceUtils.cpp
@@ -360,7 +360,7 @@
     return util::make_unique<BinaryPrimitive>(flags);
   }
 
-  for (StringPiece part : util::Tokenize(str, '|')) {
+  for (const StringPiece& part : util::Tokenize(str, '|')) {
     StringPiece trimmed_part = util::TrimWhitespace(part);
 
     bool flag_set = false;