diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index 959f2f1..e4a4099 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -1773,7 +1773,7 @@ namespace cxxopts
     parse(int argc, const char* const* argv);
 
     ParseResult
-    parse(std::string argv_str);
+    parse(const std::string& argv_str);
 
     OptionAdder
     add_options(std::string group = "");
@@ -2289,7 +2289,7 @@ Options::parse(int argc, const char* const* argv)
 
 inline
 ParseResult
-Options::parse(std::string argv_str)
+Options::parse(const std::string& argv_str)
 {
   std::vector<std::string> tokens;
   std::string token;
@@ -2299,15 +2299,14 @@ Options::parse(std::string argv_str)
     tokens.push_back(token);
   }
 
-  const char** argv = new const char*[tokens.size()];
-  for (int i = 0; i < tokens.size(); ++i) {
+  std::unique_ptr<const char*[]> argv(new const char*[tokens.size()]);
+  for (std::size_t i = 0; i < tokens.size(); ++i) {
     argv[i] = tokens[i].c_str();
   }
 
   OptionParser parser(*m_options, m_positional, m_allow_unrecognised);
 
-  auto parse_result = parser.parse(tokens.size(), argv);
-  delete argv;
+  auto parse_result = parser.parse(static_cast<int>(tokens.size()), argv.get());
   return parse_result;
 }