diff --git a/src/cookie_helper.cc b/src/cookie_helper.cc
index 87697b0a..bec1dba0 100644
--- a/src/cookie_helper.cc
+++ b/src/cookie_helper.cc
@@ -380,8 +380,7 @@ bool goodPath
 
 std::string canonicalizeHost(const std::string& host)
 {
-  std::string ch = util::toLower(host);
-  return ch;
+  return util::toLower(host);
 }
 
 bool domainMatch(const std::string& requestHost, const std::string& domain)
diff --git a/src/util.cc b/src/util.cc
index d5a3463f..8874b5b5 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -1184,16 +1184,15 @@ std::string getContentDispositionFilename(const std::string& header)
   }
 }
 
-std::string toUpper(const std::string& src) {
-  std::string temp = src;
-  uppercase(temp);
-  return temp;
+std::string toUpper(std::string src)
+{
+  uppercase(src);
+  return src;
 }
 
-std::string toLower(const std::string& src) {
-  std::string temp = src;
-  lowercase(temp);
-  return temp;
+std::string toLower(std::string src) {
+  lowercase(src);
+  return src;
 }
 
 void uppercase(std::string& s)
diff --git a/src/util.h b/src/util.h
index 07a40b7d..0f93e0de 100644
--- a/src/util.h
+++ b/src/util.h
@@ -325,9 +325,9 @@ ssize_t parse_content_disposition(char *dest, size_t destlen,
 
 std::string getContentDispositionFilename(const std::string& header);
 
-std::string toUpper(const std::string& src);
+std::string toUpper(std::string src);
 
-std::string toLower(const std::string& src);
+std::string toLower(std::string src);
 
 void uppercase(std::string& s);