diff --git a/include/argparse.hpp b/include/argparse.hpp
index f17c5b5..0c0f07b 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -319,7 +319,7 @@ class ArgumentParser {
       else
         mPositionalArguments.emplace_back(tArgument);
 
-      for (auto& mName : tArgument->mNames) {
+      for (const auto& mName : tArgument->mNames) {
         mArgumentMap.insert_or_assign(mName, tArgument);
       }
       return *tArgument;