diff --git a/libunwindstack/DwarfCfa.cpp b/libunwindstack/DwarfCfa.cpp
index 0fa1638..4ba8a4b 100644
--- a/libunwindstack/DwarfCfa.cpp
+++ b/libunwindstack/DwarfCfa.cpp
@@ -260,7 +260,7 @@
   }
 
   // Log any of the expression data.
-  for (const auto line : expression_lines) {
+  for (const auto& line : expression_lines) {
     log(indent + 1, "%s", line.c_str());
   }
   return true;
diff --git a/libunwindstack/tools/unwind_for_offline.cpp b/libunwindstack/tools/unwind_for_offline.cpp
index 640992f..c8a8ab5 100644
--- a/libunwindstack/tools/unwind_for_offline.cpp
+++ b/libunwindstack/tools/unwind_for_offline.cpp
@@ -224,7 +224,7 @@
     sp_map_start = map_info->start;
   }
 
-  for (auto frame : unwinder.frames()) {
+  for (const auto& frame : unwinder.frames()) {
     map_info = maps.Find(frame.sp);
     if (map_info != nullptr && sp_map_start != map_info->start) {
       stacks.emplace_back(std::make_pair(frame.sp, map_info->end));